Photo sensitive composition, pattern-forming method using the photosensitive composition and compound for use in the photosensitive composition

ABSTRACT

A photosensitive composition, which comprises (A) a compound capable of generating an organic acid represented by formula (I) upon irradiation with actinic ray or radiation: 
       Z-A-X—B—R—(Y) n    (I)         wherein Z represents an organic acid group; A represents a divalent linking group; X represents a divalent linking group having a hetero atom; B represents an oxygen atom or —N(R x )—; R x  represents a hydrogen atom or a monovalent organic group; R represents a monovalent organic group substituted with Y, and when B represents —N(R x )—, R and R x  may be bonded to each other to form a cyclic structure; Y represents —COOH or —CHO, and when a plurality of Y&#39;s are present, the plurality of Y&#39;s may be the same or different; and n represents an integer of from 1 to 3.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photosensitive composition capable of changing the property by reaction upon irradiation with actinic ray or radiation, a pattern-forming method using the photosensitive composition, and a compound in the photosensitive composition. More specifically, the invention relates to a photosensitive composition for use in a manufacturing process of semiconductors, e.g., IC, the manufacture of circuit substrates for liquid crystals, thermal heads and the like, and other photo-fabrication processes, lithographic printing plates, and acid-curable compositions, and also the invention relates to a pattern-forming process using the photosensitive composition, and a compound for use in the photosensitive composition.

2. Description of the Related Art

Chemical amplification resist compositions are pattern-forming materials capable of generating an acid at the area irradiated with actinic ray such as far ultraviolet ray or radiation, changing the solubility in a developing solution of the irradiated area and non-irradiated area with actinic ray or radiation by the reaction with the acid as a catalyst, and forming a pattern on a substrate.

When a KrF excimer laser is used as the exposure light source, resins having poly(hydroxystyrene) as a fundamental skeleton that is small in absorption in the region of 248 nm are mainly used, so that a high sensitivity and high resolution are secured and good pattern is formed as compared with conventionally used naphthoquinonediazide/novolak resins.

On the other hand, when a light source of further shorter wavelength, e.g., an ArF excimer laser (193 nm), is used as the exposure light source, since compounds having an aromatic group substantially show large absorption in the region of 193 nm, resists containing a resin having a highly transparent alicyclic hydrocarbon structure have been developed for an ArF excimer laser.

Various compounds have been found in connection with acid generators that are main constitutional components of chemical amplification resists, e.g., triarylsulfonium salts and arylalkylsulfonium salts are reported (e.g., refer to JP-A-2000-275845 and JP-A-10-48814).

As acids to be generated, e.g., in JP-A-2002-131897 and JP-A-2003-149812, specific organofluorosulfonic acids are used. In JP-T-11-501909 (The term “JP-T” as used herein refers to a “published Japanese translation of a PCT patent application”.), JP-A-2002-268223 and JP-A-2003-246786, imido anionic acid generators capable of generating highly acidic imido upon irradiation with actinic ray or radiation are used.

However, these compounds are still insufficient in various points and the improvement in line edge roughness, exposure latitude and the like is required.

As a technique of enhancing resolution in the optical microscope, a method of filling in between a projection lens and a sample with a liquid having a high refractive index (hereinafter referred to as “immersion liquid”), i.e., an immersion method, is conventionally known.

As “the effect of immersion”, resolution and the depth of focus in the case of immersion can be expressed by the following expressions, with λ₀ as the wavelength of the exposure light in the air, n as the refractive index of immersion liquid to the air, and when NA₀= sin θ with θ as convergence half angle of the ray of light:

Resolution=k ₁·(λ₀ /n)/NA ₀

Depth of focus=±k ₂·(λ₀ /n)/NA ₀ ²

That is, the effect of immersion is equivalent to the case of using exposure wavelength of the wavelength of 1/n. In other words, in the case of the projection optical system of the same NA, the depth of focus can be made n times by immersion. This is effective for every pattern form, and further, it is possible to combine an immersion method with super resolution techniques such as a phase shift method and a transformation lighting method now under discussion.

The examples of the apparatus applying this effect to the transfer of a micro-fine image pattern of a semiconductor element are introduced in JP-A-57-153433 (the term “JP-A” as used herein refers to an “unexamined published Japanese patent application”) and JP-A-7-220990.

The latest technical advancement of immersion exposure is reported in SPIE Proc., 4688, 11 (2002), J. Vac. Sci. Tecnol. B, 17 (1999), SPIE Proc., 3999, 2 (2000), and WO 2004/077158. When an ArF excimer laser is used as the light source, it is thought that pure water (having a refractive index of 1.44 at 193 nm) is most promising as the immersion liquid in the light of the safety in handling, the transmittance and the refractive index at 193 nm. When an F₂ excimer laser is used as the light source, a solution containing fluorine is discussed from the balance of transmittance and refractive index at 157 nm, but a sufficiently satisfactory solution from the viewpoint of the environmental safety and at the point of refractive index has not been found yet. From the extent of the effect of immersion and the degree of completion of resist, it is thought that immersion exposure technique will be carried on an ArF exposure apparatus earliest.

It is appointed that when a chemical amplification resist is applied to immersion exposure, the resist layer will be brought into contact with the immersion liquid at the time of exposure, so that the resist layer decomposes and ingredients that adversely influence the immersion liquid ooze out of the resist layer. WO 2004/068242 discloses examples that resist performance decomposes by the immersion of a resist for ArF exposure in water before and after exposure and appoints this is a problem in immersion exposure.

SUMMARY OF THE INVENTION

A first object of the invention is to provide a photosensitive composition showing good pattern profile and pattern collapse resistance, and improved in sensitivity and dissolution contrast in EUV ray exposure. A second object of the invention is to provide a pattern-forming method using the photosensitive composition. A third object is to provide a positive resist composition suitable for immersion exposure that shows good performances as described above even in immersion exposure. A fourth object is to provide a pattern-forming method using the positive resist composition. A fifth object is to provide a compound capable of generating a specific organic acid upon irradiation with actinic ray or radiation that is added to the photosensitive composition.

The present invention is as follows.

(1) A photosensitive composition, which comprises (A) a compound capable of generating an organic acid represented by formula (I) upon irradiation with actinic ray or radiation:

Z-A-X—B—R—(Y)_(n)  (I)

wherein Z represents an organic acid group;

A represents a divalent linking group;

X represents a divalent linking group having a hetero atom;

B represents an oxygen atom or —N(R_(x))—;

R_(x) represents a hydrogen atom or a monovalent organic group;

R represents a monovalent organic group substituted with Y, and when B represents —N(R_(x))—, R and R_(x) may be bonded to each other to form a cyclic structure;

Y represents —COOH or —CHO, and when a plurality of Y's are present, the plurality of Y's may be the same or different; and

n represents an integer of from 1 to 3.

(2) The photosensitive composition as described in (1) above,

wherein A contains a fluorine atom.

(3) The photosensitive composition as described in (1) or (2) above,

wherein Z is a sulfo group or a carboxyl group.

(4) The photosensitive composition as described in any of (1) to (3) above,

wherein X is selected from the group consisting of —SO₂—, —SO— and —CO—.

(5) The photosensitive composition as described in any of (1) to (4) above,

wherein the compound capable of generating an organic acid represented by formula (I) upon irradiation with actinic ray or radiation is a sulfonium salt compound of an organic acid represented by formula (I) or an iodonium salt compound of an organic acid represented by formula (I).

(6) A pattern-forming method, which comprises:

forming a photosensitive film with a photosensitive composition as described in any of (1) to (5) above; and

exposing and developing the photosensitive film.

(7) An organic acid represented by formula (I) and a metal salt thereof:

Z-A-X—B—R—(Y)_(n)  (I)

wherein Z represents an organic acid group;

A represents a divalent linking group;

X represents a divalent linking group having a hetero atom;

B represents an oxygen atom or —N(R_(x))—;

R_(x) represents a hydrogen atom or a monovalent organic group;

R represents a monovalent organic group substituted with Y, and when B represents —N(R_(x))—, R and R_(x) may be bonded to each other to form a cyclic structure;

Y represents —COOH or —CHO, and when a plurality of Y's are present, the plurality of Y's may be the same or different; and

n represents an integer of from 1 to 3.

(8) A sulfonium salt compound of an organic acid represented by formula (I) or an iodonium salt compound of an organic acid represented by formula (I):

Z-A-X—B—R—(Y)_(n)  (I)

wherein Z represents an organic acid group;

A represents a divalent linking group;

X represents a divalent linking group having a hetero atom;

B represents an oxygen atom or —N(R_(x))—;

R_(x) represents a hydrogen atom or a monovalent organic group;

R represents a monovalent organic group substituted with Y, and when B represents —N(R_(x))—, R and R_(x) may be bonded to each other to form a cyclic structure;

Y represents —COOH or —CHO, and when a plurality of Y's are present, the plurality of Y's may be the same or different; and

n represents an integer of from 1 to 3.

As preferred embodiments of the invention, the following constitutions are exemplified.

(9) The photosensitive composition as described in any of (1) to (5) above, which further comprises (B) a compound capable of generating an acid other than an organic acid represented by formula (I) upon irradiation with actinic ray or radiation.

(10) The photosensitive composition as described in (9) above,

wherein the compound of component (B) is a sulfonium salt of a fluorine-substituted alkanesulfonic acid, a fluorine-substituted benzenesulfonic acid or a fluorine-substituted imidic acid.

(11) The positive photosensitive composition as described in any of (1) to (5), (9) and (10) above, which further comprises (C) a resin capable of decomposing by an action of an acid to increase solubility in an alkali developing solution.

(12) The positive photosensitive composition as described in (11) above,

wherein the resin of component (C) has a fluorine atom on a main chain or a side chain.

(13) The positive photosensitive composition as described in (11) above,

wherein the resin of component (C) has a hexafluoroisopropanol structure.

(14) The positive photosensitive composition as described in (11) above,

wherein the resin of component (C) has a hydroxystyrene structural unit.

(15) The positive photosensitive composition as described in (11) above,

wherein the resin of component (C) has at least one repeating unit selected from the group consisting of 2-alkyl-2-adamantyl(meth)acrylate and dialkyl(1-adamantyl)methyl(meth)acrylate.

(16) The positive photosensitive composition as described in (11) above,

wherein the resin of component (C) has a monocyclic or polycyclic alicyclic hydrocarbon structure.

(17) The positive photosensitive composition as described in (16) above,

wherein the resin of component (C) has at least one repeating unit selected from the group consisting of 2-alkyl-2-adamantyl(meth)acrylate and dialkyl(1-adamantyl)methyl(meth)acrylate, at least one repeating unit having a lactone structure and at least one repeating unit having a hydroxyl group.

(18) The positive photosensitive composition as described in (17) above,

wherein the resin of component (C) further has a repeating unit having a carboxyl group.

(19) The positive photosensitive composition as described in (11) above,

wherein the resin of component (C) has a silicon atom on a main chain or a side chain.

(20) The positive photosensitive composition as described in (11) above,

wherein the resin of component (C) has a repeating unit having a lactone structure.

(21) The positive photosensitive composition as described in any of (11) to (20) above, which further comprises (D) a dissolution inhibiting compound capable of decomposing by an action of an acid to increase solubility in an alkali developing solution, and having a molecular weight of 3,000 or less.

(22) The positive photosensitive composition as described in any of (1) to (5), (9) and (10) above, which further comprises: (E) a resin soluble in an alkali developing solution; and (D) a dissolution inhibiting compound capable of decomposing by an action of an acid to increase solubility in an alkali developing solution, and having a molecular weight of 3,000 or less.

(23) The negative photosensitive composition as described in any of (1) to (5), (9) and (10) above, which further comprises: (E) a resin soluble in an alkali developing solution; and (F) an acid crosslinking agent capable of crosslinking with the resin soluble in an alkali developing solution by an action of an acid.

(24) The photosensitive composition as described in any of (1) to (5) and (9) to (23) above, which further comprises at least one of (G) a basic compound and (H) a fluorine and/or silicon surfactant.

(25) The photosensitive composition as described in (24) above,

wherein the basic compound (G) is a compound having a structure selected from the group consisting of an imidazole structure, a diazabicyclo structure, an onium hydroxide structure, an onium carboxylate structure, a trialkylamine structure, an aniline structure and a pyridine structure, an alkylamine derivative having at least one of a hydroxyl group and an ether bond or an aniline derivative having at least one of a hydroxyl group and an ether bond.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in detail below.

In the description of a group (an atomic group) in the specification of the invention, the description not referring to substitution or unsubstitution includes both a group not having a substituent and a group having a substituent. For example, “an alkyl group” includes not only an alkyl group having no substituent (an unsubstituted alkyl group) but also an alkyl group having a substituent (a substituted alkyl group).

A positive photosensitive composition in the invention, preferably a positive resist composition, contains (A) a compound capable of generating an organic acid represented by formula (I), and (C) a resin capable of decomposing by the action of an acid to increase solubility in an alkali developing solution, and if necessary, further contains (B) a compound capable of generating an acid upon irradiation with actinic ray or radiation, and (D) a dissolution inhibiting compound capable of decomposing by the action of an acid to increase solubility in an alkali developing solution, and having a molecular weight of 3,000 or less, alternatively, contains (A) a compound capable of generating an organic acid represented by formula (I), (E) a resin soluble in an alkali developing solution, and (D) a dissolution inhibiting compound capable of decomposing by the action of an acid to increase solubility in an alkali developing solution, and having a molecular weight of 3,000 or less, and if necessary, further contains (B) a compound capable of generating an acid upon irradiation with actinic ray or radiation.

A negative photosensitive composition in the invention, preferably a negative resist composition, contains (A) a compound capable of generating an organic acid represented by formula (I), (E) a resin soluble in an alkali developing solution, and (F) an acid crosslinking agent capable of crosslinking with the resin soluble in an alkali developing solution by the action of an acid, and if necessary, further contains (B) a compound capable of generating an acid upon irradiation with actinic ray or radiation.

[1] (A) A compound capable of generating an organic acid represented by formula (I) upon irradiation with actinic ray or radiation:

A photosensitive composition in the invention contains a compound capable of generating an organic acid represented by the following formula (I) upon irradiation with actinic ray or radiation (also referred to as “compound (A)”).

Z-A-X—B—R—(Y)_(n)  (I)

In formula (I), Z represents an organic acid group; A represents a divalent linking group; X represents a divalent linking group having a hetero atom; B represents an oxygen atom or —N(R_(x))—; R_(x) represents a hydrogen atom or a monovalent organic group; R represents a monovalent organic group substituted with Y; when B represents —N(R_(x))—, R and R_(x) may be bonded to each other to form a cyclic structure; Y represents either —COOH or —CHO; and n represents an integer of from 1 to 3.

The divalent linking group represented by A is preferably a divalent organic group having from 1 to 8 carbon atoms, e.g., an alkylene group, a phenylene group, etc., are exemplified. The divalent linking group as A is more preferably an alkylene group, and the carbon atom number is preferably from 1 to 6, and more preferably from 1 to 4. A linking group such as an oxygen atom or a sulfur atom may be contained in the alkylene chain. The alkylene group may be substituted with a fluorine atom, and in that case, an alkylene group in which from 30 to 100% of the hydrogen atom number is substituted with fluorine atoms is preferred, and it is more preferred for the carbon atom bonding to Z moiety to have a fluorine atom. Further, a perfluoroalkylene group is preferred, and a perfluoro-methylene group, a perfluoroethylene group, a perfluoro-propylene group and a perfluorobutylene group are most preferred, by which sensitivity is increased.

As the organic acid group represented by Z, e.g., a sulfo group, a carboxyl group, etc., are exemplified, and a sulfo group is preferred, by which sensitivity is increased.

As the divalent linking group having a hetero atom represented by X, the total carbon atom number is preferably from 1 to 6, and more preferably from 2 to 4. As the hetero atoms, e.g., an oxygen atom, a sulfur atom, a nitrogen atom and a halogen atom are exemplified, and an oxygen atom and a sulfur atom are more preferred. X preferably represents —SO₂—, —SO— or —CO—.

The monovalent organic group substituted with Y represented by R is preferably a monovalent organic group having from 4 to 30 carbon atoms, e.g., an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkenyl group, an alkoxyl group, an alkoxycarbonylamino group, etc., can be exemplified.

Y represents —COOH or —CHO. In a case where a plurality of Y's are present, these plurality of Y's may be the same or different.

The alkyl group as organic group R may have a substituent, and the alkyl group is preferably a straight chain or branched alkyl group having from 1 to 30 carbon atoms, and an oxygen atom, a sulfur atom, or a nitrogen atom may be contained in the alkyl chain. Specifically, straight chain alkyl groups, e.g., a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-dodecyl group, an n-tetradecyl group, and an n-octadecyl group, and branched alkyl groups, e.g., an isopropyl group, an isobutyl group, a t-butyl group, a neopentyl group, and a 2-ethylhexyl group are exemplified.

The cycloalkyl group as organic group R may have a substituent, and the cycloalkyl group is preferably a cycloalkyl group having from 3 to 20 carbon atoms, which may be polycyclic and may have an oxygen atom in the ring. Specifically, a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, and an adamantyl group can be exemplified.

The aryl group as organic group R may have a substituent, and the aryl group is preferably an aryl group having from 6 to 14 carbon atoms, e.g., a phenyl group and a naphthyl group can be exemplified.

The aralkyl group as organic group R may have a substituent, and the aralkyl group is preferably an aralkyl group having from 7 to 20 carbon atoms, e.g., a benzyl group, a phenethyl group, a naphthylmethyl group, and a naphthylethyl group can be exemplified.

As the alkenyl group as organic group R, a group having a double bond on an arbitrary position of the above alkyl group and cycloalkyl group can be exemplified.

The alkoxyl group, and the alkoxyl group in the alkoxycarbonylamino group as organic group R is preferably an alkoxyl group having from 1 to 30 carbon atoms, e.g., a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, a pentyloxy group, a hexyloxy group, and a heptyloxy group can be exemplified.

The monovalent organic group represented by R_(x) is a monovalent organic group preferably having from 1 to 40 carbon atoms, and more preferably from 4 to 30 carbon atoms, e.g., an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkenyl group, an alkoxyl group, an alkoxycarbonyl-amino group, a cyano group, etc., can be exemplified. In a case where a plurality of R_(x)'s are present, these plurality of R_(x)'s may be the same or different. The details of the monovalent organic group represented by R_(x) are the same as in R above.

When B represents —N(R_(x))—, R and R_(x) may be bonded to each other to form a cyclic structure. Stability is improved by forming a cyclic structure, so that the preservation stability of the composition using this compound is bettered. The carbon atom number of the ring to be formed is preferably from 4 to 20, which ring may be monocyclic or polycyclic.

When organic group R is bonded to an aryl group, an aralkyl group or R_(x) to form a ring, organic group R and/or organic group R_(x) preferably have substituent Q. As substituents Q, e.g., a halogen atom, a nitro group, a cyano group, a carbonyl group, an alkyl group (preferably having from 3 to 15 carbon atoms), a cycloalkyl group (preferably having from 3 to 10 carbon atoms), an aryl group (preferably having from 6 to 14 carbon atoms), an alkoxyl group (preferably having from 1 to 10 carbon atoms), and an acyl group (preferably having from 2 to 20 carbon atoms) can be exemplified. More preferred substituents Q are a halogen atom, a nitro group, a cyano group, an alkyl group, a cycloalkyl group, an alkoxyl group, and an acyl group. The number of substituents is preferably 1 or more, and the position of substitution is preferably on a carbon contiguous to the carbon bonding to B, by which the solubility of solvents increases.

The sulfonic acid represented by formula (I) is preferably represented by any of the following formulae (I-a) to (I-d).

The organic acid represented by formula (I) can be synthesized according to general sulfonic acid esterification reaction or sulfonamidation reaction. For example, the organic acid represented by formula (I) can be obtained by a method of reacting a sulfonyl halide portion of one side of a bis-sulfonyl halide compound selectively with amine, alcohol and the like containing a partial structure represented by formula (I) to form a sulfonamido bond, a sulfonic ester bond, and then hydrolyzing a sulfonyl halide portion of the other side, or by a method of ring opening reaction of cyclic sulfonic acid anhydride with amine and alcohol containing a partial structure represented by formula (I). The amine and alcohol containing a partial structure represented by formula (I) can be synthesized by the reaction of amine and alcohol with anhydride such as (R'O₂C)₂O or R'O₂CCl, and an acid chloride compound in the presence of a base.

Compound (A) can be easily synthesized from the compound represented by formula (I), or a lithium, sodium, or potassium salt of the compound, and hydroxide, bromide or chloride of iodonium or sulfonium according to the salt exchange method disclosed in JP-T-11-501909 or JP-A-2003-246786.

Compound (A) is preferably a sulfonium salt compound or iodonium salt compound of the organic acid represented by formula (I), and more preferably a compound represented by the following formula (A1) or (A2).

In formula (A1), R₂₀₁, R₂₀₂ and R₂₀₃ each independently represents an organic group; and X⁻ represents an anion of the organic acid represented by formula (I).

The number of carbon atoms of the organic groups represented by R₂₀₁, R₂₀₂ and R₂₀₃ is generally from 1 to 30, and preferably from 1 to 20.

Any two of R₂₀₁, R₂₀₂ and R₂₀₃ may be bonded to each other to form a cyclic structure, and an oxygen atom, a sulfur atom, an ester bond, an amido bond or a carbonyl group may be contained in the ring. As the group formed by bonding any two of R₂₀₁, R₂₀₂ and R₂₀₃, an alkylene group (e.g., a butylene group and a pentylene group) can be exemplified.

As the specific examples of the organic groups represented by R₂₀₁, R₂₀₂ and R₂₀₃, the corresponding groups in compounds (A1a), (A1b) and (A1c) described later can be exemplified.

The compound represented by formula (A1) may be a compound having a plurality of structures represented by formula (A1). For example, the compound represented by formula (A1) may be a compound having a structure that at least one of R₂₀₁, R₂₀₂ and R₂₀₃ of the compound represented by formula (A1) is bonded to at least one of R₂₀₁, R₂₀₂ and R₂₀₃ of another compound represented by formula (A1).

The following compounds (A1a), (A1b) and (A1c) can be exemplified as more preferred components (A1).

Compound (A1a) is an arylsulfonium compound in which at least one of R₂₀₁, R₂₀₂ and R₂₀₃ in formula (A1) represents an aryl group, that is, a compound having arylsulfonium as a cation.

All of R₂₀₁, R₂₀₂ and R₂₀₃ of the arylsulfonium compound may be aryl groups, or a part of R₂₀₁, R₂₀₂ and R₂₀₃ may be an aryl group and the remainder may be an alkyl group or a cycloalkyl group.

As the arylsulfonium compound, e.g., a triarylsulfonium compound, a diarylalkylsulfonium compound, a diarylcyclo-alkylsulfonium compound, an aryldialkylsulfonium compound, an aryldicycloalkylsulfonium compound, and an arylalkylcyclo-alkylsulfonium compound can be exemplified.

As the aryl group of the arylsulfonium compound, an aryl group consisting of hydrocarbon, and a heteroaryl group having a hetero atom, such as a nitrogen atom, a sulfur atom, or an oxygen atom are exemplified. As the aryl groups consisting of hydrocarbon, a phenyl group and a naphthyl group are preferred, and a phenyl group is more preferred. As the heteroaryl groups, e.g., a pyrrole group, an indole group, a carbazole group, a furan group, a thiophene group, etc., are exemplified, and an indole group is preferred. When the arylsulfonium compound has two or more aryl groups, these two or more aryl groups may be the same or different.

The alkyl group that the arylsulfonium compound may have according to necessity is preferably a straight chain or branched alkyl group having from 1 to 15 carbon atoms, e.g., a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, and a t-butyl group can be exemplified.

The cycloalkyl group that the arylsulfonium compound may have according to necessity is preferably a cycloalkyl group having from 3 to 15 carbon atoms, e.g., a cyclopropyl group, a cyclobutyl group and a cyclohexyl group can be exemplified.

The aryl group, alkyl group and cycloalkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ may have a substituent, e.g., an alkyl group (e.g., having from 1 to 15 carbon atoms), a cycloalkyl group (e.g., having from 3 to 15 carbon atoms), an aryl group (e.g., having from 6 to 14 carbon atoms), an alkoxyl group (e.g., having from 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, and a phenylthio group are exemplified as the examples of the substituents. The preferred substituents are a straight chain or branched alkyl group having from 1 to 12 carbon atoms, a cycloalkyl group having from 3 to 12 carbon atoms, and a straight chain, branched, or cyclic alkoxyl group having from 1 to 12 carbon atoms, and the especially preferred substituents are an alkyl group having from 1 to 4 carbon atoms and an alkoxyl group having from 1 to 4 carbon atoms. The substituent may be substituted on any one of three of R₂₀₁, R₂₀₂ and R₂₀₃, or may be substituted on all of the three. When R₂₀₁, R₂₀₂ and R₂₀₃ each independently represents an aryl group, it is preferred that the substituent be substituted on the p-position of the aryl group.

Compound (A1b) is described below.

Compound (A1b) is a compound in the case where R₂₀₁, R₂₀₂ and R₂₀₃ in formula (A1) each independently represents an organic group not having an aromatic ring. The aromatic ring here also includes an aromatic ring having a hetero atom.

The organic group not having an aromatic ring represented by R₂₀₁, R₂₀₂ and R₂₀₃ generally has from 1 to 30 carbon atoms, and preferably from 1 to 20 carbon atoms.

R₂₀₁, R₂₀₂ and R₂₀₃ each preferably represents an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group, more preferably represents a straight chain or branched 2-oxoalkyl group, a 2-oxocycloalkyl group, or an alkoxy-carbonylmethyl group, and especially preferably a straight chain or branched 2-oxoalkyl group.

The alkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ may be either straight chain or branched, and is preferably a straight chain or branched alkyl group having from 1 to 20 carbon atoms, e.g., a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group can be exemplified. As the alkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃, more preferably a straight chain or branched 2-oxoalkyl group, and an alkoxycarbonylmethyl group can be exemplified.

The cycloalkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ is preferably a cycloalkyl group having from 3 to 10 carbon atoms, e.g., a cyclopentyl group, a cyclohexyl group and a norbonyl group can be exemplified. The cycloalkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ is more preferably a 2-oxocycloalkyl group.

As the straight chain or branched 2-oxoalkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ may have a double bond in the ring, and preferably a group having >C═O at the 2-position of the above alkyl group can be exemplified.

As the 2-oxocycloalkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ may have a double bond in the ring, and preferably a group having >C═O at the 2-position of the above cycloalkyl group can be exemplified.

As the alkoxyl group in the alkoxycarbonylmethyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃, preferably an alkoxyl group having from 1 to 5 carbon atoms, e.g., a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a pentoxy group can be exemplified.

R₂₀₁, R₂₀₂ and R₂₀₃ may further be substituted with a halogen atom, an alkoxyl group (e.g., having from 1 to 5 carbon atoms), an alkoxycarbonyl group (e.g., having from 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.

Compound (A1c) is a compound represented by the following formula (A1c) and has an arylacylsulfonium salt structure.

In formula (A1c), R₂₁₃ represents an aryl group that may have a substituent, and the aryl group is preferably a phenyl group or a naphthyl group. As preferred substituents on R₂₁₃, an alkyl group, an alkoxyl group, an acyl group, a nitro group, a hydroxyl group, an alkoxycarbonyl group, and a carboxyl group are exemplified.

R₂₁₄ and R₂₁₅ each independently represents a hydrogen atom, an alkyl group or a cycloalkyl group.

Y₂₀₁ and Y₂₀₂ each independently represents an alkyl group, a cycloalkyl group, an aryl group, or a vinyl group.

X⁻ represents an anion of the organic acid represented by formula (I).

R₂₁₃ and R₂₁₄ may be bonded to each other to form a cyclic structure, R₂₁₄ and R₂₁₅ may be bonded to each other to form a cyclic structure, and Y₂₀₁ and Y₂₀₂ may be bonded to each other to form a cyclic structure. These cyclic structures may contain an oxygen atom, a sulfur atom, an ester bond, and an amido bond. As the groups formed by bonding R₂₁₃ and R₂₁₄, R₂₁₄ and R₂₁₅, and Y₂₀₁ and Y₂₀₂, a butylene group, a pentylene group, and the like can be exemplified.

The alkyl group represented by R₂₁₄, R₂₁₅, Y₂₀₁ and Y₂₀₂ is preferably a straight chain or branched alkyl group having from 1 to 20 carbon atoms. The alkyl group represented by Y₂₀₁ and Y₂₀₂ is preferably a 2-oxoalkyl group having >C═O at the 2-position of the alkyl group, or an alkoxycarbonylalkyl group (preferably an alkoxyl group having from 2 to 20 carbon atoms), and more preferably a carboxyalkyl group.

The cycloalkyl group represented by R₂₁₄, R₂₁₅, Y₂₀₁ and Y₂₀₂ is preferably a cycloalkyl group having from 3 to 20 carbon atoms.

Y₂₀₁ and Y₂₀₂ each preferably represents an alkyl group having 4 or more carbon atoms, more preferably an alkyl group having from 4 to 6 carbon atoms, and still more preferably an alkyl group having from 4 to 12 carbon atoms.

It is preferred that at least one of R₂₁₄ and R₂₁₅ represents an alkyl group, and more preferably both R₂₁₄ and R₂₁₅ represent an alkyl group.

In formula (A2), R₂₀₄ and R₂₀₅ each independently represents an aryl group, an alkyl group, or a cycloalkyl group.

X⁻ represents an anion of the organic acid represented by formula (I).

As the aryl group represented by R₂₀₄ and R₂₀₅, an aryl group consisting of hydrocarbon, and a heteroaryl group having a hetero atom, such as a nitrogen atom, a sulfur atom, or an oxygen atom are exemplified. As the aryl groups consisting of hydrocarbon, a phenyl group and a naphthyl group are preferred, and a phenyl group is more preferred. As the heteroaryl groups, e.g., a pyrrole group, an indole group, a carbazole group, a furan group, a thiophene group, etc., are exemplified, and an indole group is preferred.

The alkyl group represented by R₂₀₄ and R₂₀₅ may be either straight chain or branched, and preferably a straight chain or branched alkyl group having from 1 to 10 carbon atoms, e.g., a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group can be exemplified.

The cycloalkyl group represented by R₂₀₄ and R₂₀₅ is preferably a cycloalkyl group having from 3 to 10 carbon atoms, e.g., a cyclopentyl group, a cyclohexyl group, and a norbonyl group can be exemplified.

R₂₀₄ and R₂₀₅ may have a substituent. As the substituents that R₂₀₄ and R₂₀₅ may have, e.g., an alkyl group (e.g., having from 1 to 15 carbon atoms), a cycloalkyl group (e.g., having from 3 to 15 carbon atoms), an aryl group (e.g., having from 6 to 15 carbon atoms), an alkoxyl group (e.g., having from 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, and a phenylthio group can be exemplified.

Compound (A) is preferably a compound represented by formula (A1), and more preferably a compound represented by formula (A1a), (A1b) or (A1c).

The specific examples of organic acids represented by formula (I), i.e., the specific examples of the anionic parts in compound (A) (anions are organic acid groups corresponding to Z in formula (I)) are shown below, but the invention is not restricted thereto.

The specific examples of the cationic parts in compound (A) are shown below, but the invention is not restricted thereto.

The specific examples of compound (A) are shown in Table 1 below, but the invention is not restricted thereto.

TABLE 1 Anionic Cationic Structure Structure (X⁻) Compound (A) I-1 X1 A-1 I-1 X2 A-2 I-1 X3 A-3 I-1 X4 A-4 I-1 X5 A-5 I-1 X6 A-6 I-1 X7 A-7 I-1 X8 A-8 I-1 X9 A-9 I-1 X10 A-10 I-1 X11 A-11 I-1 X12 A-12 I-1 X13 A-13 I-1 X14 A-14 I-1 X15 A-15 I-1 X16 A-16 I-1 X17 A-17 I-1 X18 A-18 I-1 X19 A-19 I-1 X20 A-20 I-1 X21 A-21 I-1 X22 A-22 I-1 X23 A-23 I-1 X24 A-24 I-1 X25 A-25 I-1 X26 A-26 I-1 X27 A-27 I-1 X28 A-28 I-1 X29 A-29 I-2 X1 A-30 I-2 X2 A-31 I-2 X4 A-32 I-2 X6 A-33 I-2 X8 A-34 I-2 X9 A-35 I-2 X10 A-36 I-2 X15 A-37 I-2 X17 A-38 I-2 X25 A-39 I-4 X1 A-40 I-4 X2 A-41 I-4 X4 A-42 I-8 X6 A-43 I-8 X8 A-44 I-8 X9 A-45 I-9 X10 A-46 I-9 X15 A-47 I-9 X17 A-48 I-10 X25 A-49 I-10 X1 A-50 I-10 X2 A-51 I-12 X4 A-52 I-12 X6 A-53 I-12 X8 A-54 I-25 X9 A-55 I-25 X10 A-56 I-25 X15 A-57 I-25 X17 A-58 I-26 X25 A-59 I-26 X1 A-60 I-26 X2 A-61 I-27 X4 A-62 I-27 X6 A-63 I-27 X8 A-64 I-28 X9 A-65 I-28 X10 A-66 I-29 X15 A-67 I-29 X17 A-68 I-30 X25 A-69 I-31 X1 A-70 I-31 X2 A-71 I-31 X4 A-72 I-31 X6 A-73 I-32 X8 A-74 I-31 X9 A-75 I-31 X10 A-76 I-33 X15 A-77 I-33 X17 A-78 I-33 X25 A-79 I-33 X1 A-80 I-33 X2 A-81 I-33 X4 A-82 I-33 X6 A-83 I-3 X18 A-84 I-5 X19 A-85 I-5 X20 A-86 I-5 X21 A-87 I-6 X22 A-88 I-7 X23 A-89 I-11 X24 A-90 I-13 X26 A-91 I-14 X27 A-92 I-15 X28 A-93 I-16 X29 A-94 I-17 X11 A-95 I-18 X12 A-96 I-19 X13 A-97 I-20 X14 A-98 I-21 X16 A-99 I-22 X3 A-100 I-23 X1 A-101 I-24 X5 A-102 I-24 X6 A-103 I-16 X6 A-104 I-1 X30 A-105 I-1 X31 A-106 I-1 X32 A-107

Compound (A) can be easily synthesized from the compound represented by formula (I), or a lithium, sodium, or potassium salt of the compound, and hydroxide, bromide or chloride of iodonium or sulfonium according to the salt exchange method disclosed in JP-T-11-501909 or JP-A-2003-246786.

The content of compound (A) in the photosensitive composition in the invention is preferably from 0.1 to 20 mass % based on the solids content of the composition, and more preferably from 0.1 to 10 mass %. (In this specification, mass ratio is equal to weight ratio.)

[2] (B) A compound capable of generating an acid upon irradiation with actinic ray or radiation:

It is preferred for the photosensitive composition in the invention to further contain a compound capable of generating an acid upon irradiation with actinic ray or radiation (hereinafter also referred to as “an acid generator usable in combination”) besides compound (A).

As acid generators usable in combination, photoinitiators of photocationic polymerization, photoinitiators of photoradical polymerization, photo-decoloring agents and photo-discoloring agents of dyestuffs, well-known compounds capable of generating an acid upon irradiation with actinic ray or radiation that are used in micro-resists and the like, and the mixtures of these compounds can be optionally selected and used.

For example, diazonium salt, phosphonium salt, sulfonium salt, iodonium salt, imidosulfonate, oximesulfonate, diazodisulfone, disulfone, and o-nitrobenzylsulfonate are exemplified.

Further, compounds obtained by introducing a group or a compound capable of generating an acid upon irradiation with actinic ray or radiation to the main chain or side chain of polymers, for example, the compounds disclosed in U.S. Pat. No. 3,849,137, German Patent 3,914,407, JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038, JP-A-63-163452, JP-A-62-153853, JP-A-63-146029, etc., can be used.

The compounds generating an acid by the action of lights as disclosed in U.S. Pat. No. 3,779,778, EP 126712, etc., can also be used.

As a preferred acid generator usable in combination, a compound represented by the following formula (ZI), (ZII) or (ZIII) can be exemplified.

In formula (ZI), R₂₀₁, R₂₀₂ and R₂₀₃ each independently represents an organic group.

The number of carbon atoms of the organic groups represented by R₂₀₁, R₂₀₂ and R₂₀₃ is generally from 1 to 30, and preferably from 1 to 20.

Two of R₂₀₁, R₂₀₂ and R₂₀₃ may be bonded to each other to form a cyclic structure, and an oxygen atom, a sulfur atom, an ester bond, an amido bond or a carbonyl group may be contained in the ring. As the group formed by bonding two of R₂₀₁, R₂₀₂ and R₂₀₃, an alkylene group (e.g., a butylene group, a pentylene group) can be exemplified.

X⁻ represents a non-nucleophilic anion.

The examples of the non-nucleophilic anions represented by X⁻ include, e.g., a sulfonate anion, a carboxylate anion, a sulfonylimide anion, a bis(alkylsulfonyl)imide anion, and a tris(alkylsulfonyl)methyl anion.

A non-nucleophilic anion is an anion having extremely low ability of causing a nucleophilic reaction and capable of restraining the aging decomposition due to an intramolecular nucleophilic reaction, so that the aging stability of a resist can be improved with a non-nucleophilic anion.

As sulfonate anions, e.g., an aliphatic sulfonate anion, an aromatic sulfonate anion and a camphor sulfonate anion are exemplified.

As carboxylate anions, e.g., an aliphatic carboxylate anion, an aromatic carboxylate anion and an aralkylcarboxylate anion are exemplified.

The aliphatic moiety in the aliphatic sulfonate anion may be an alkyl group or a cycloalkyl group, preferably an alkyl group having from 1 to 30 carbon atoms and a cycloalkyl group having from 3 to 30 carbon atoms, e.g., a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a pentyl group, a neopentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an eicosyl group, a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, an adamantyl group, a norbonyl group, and a boronyl group are exemplified.

The aromatic group in the aromatic sulfonate anion is preferably an aryl group having from 6 to 14 carbon atoms, e.g., a phenyl group, a tolyl group, and a naphthyl group are exemplified.

The alkyl group, cycloalkyl group and aryl group in the aliphatic sulfonate anion and aromatic sulfonate anion may have a substituent. As the substituents of the alkyl group, cycloalkyl group and aryl group in the aliphatic sulfonate anion and aromatic sulfonate anion, e.g., a nitro group, a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom), a carboxyl group, a hydroxyl group, an amino group, a cyano group, an alkoxyl group (preferably having from 1 to 15 carbon atoms), a cycloalkyl group (preferably having from 3 to 15 carbon atoms), an aryl group (preferably having from 6 to 14 carbon atoms), an alkoxycarbonyl group (preferably having from 2 to 7 carbon atoms), an acyl group (preferably having from 2 to 12 carbon atoms), an alkoxycarbonyloxy group (preferably having from 2 to 7 carbon atoms), an alkylthio group (preferably having from 1 to 15 carbon atoms), an alkylsulfonyl group (preferably having from 1 to 15 carbon atoms), an alkyliminosulfonyl group (preferably having from 2 to 15 carbon atoms), an aryloxysulfonyl group (preferably having from 6 to 20 carbon atoms), an alkylaryloxysulfonyl group (preferably having from 7 to 20 carbon atoms), a cycloalkylaryloxysulfonyl group (preferably having from 5 to 20 carbon atoms), and a cycloalkylalkyloxyalkyloxy group (preferably having from 8 to 20 carbon atoms) are exemplified. As for the aryl group and the cyclic structure of each group, an alkyl group (preferably having from 1 to 15 carbon atoms) can be further exemplified as the substituent.

As the aliphatic moiety in the aliphatic carboxylate anion, the same alkyl group and cycloalkyl group as in the aliphatic sulfonate anion can be exemplified.

As the aromatic group in an aromatic carboxylate anion, the same aryl group as in the aromatic sulfonate anion can be exemplified.

As the aralkyl group in the aralkylcarboxylate anion, preferably an aralkyl group having from 6 to 12 carbon atoms, e.g., a benzyl group, a phenethyl group, a naphthylmethyl group, a naphthylethyl group, and a naphthylmethyl group can be exemplified.

The alkyl group, cycloalkyl group, aryl group and aralkyl group in the aliphatic carboxylate anion, aromatic carboxylate anion and aralkylcarboxylate anion may have a substituent. As the substituents of the alkyl group, cycloalkyl group, aryl group and aralkyl group in the aliphatic carboxylate anion, aromatic carboxylate anion and aralkylcarboxylate anion, e.g., the same halogen atom, alkyl group, cycloalkyl group, alkoxyl group and alkylthio group as in the aromatic sulfonate anion can be exemplified.

As the sulfonylimide anion, e.g., a saccharin anion can be exemplified.

The alkyl group in the bis(alkylsulfonyl)imide anion and tris(alkylsulfonyl)methyl anion is preferably an alkyl group having from 1 to 5 carbon atoms, e.g., a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a pentyl group and a neopentyl group are exemplified. As the substituents on these alkyl groups, a halogen atom, an alkyl group substituted with a halogen atom, an alkoxyl group, an alkylthio group, an alkyloxysulfonyl group, an aryloxysulfonyl group, and a cycloalkylaryloxysulfonyl group can be exemplified, and an alkyl group substituted with a fluorine atom is preferred.

As other non-nucleophilic anions, e.g., fluorinated phosphorus, fluorinated boron and fluorinated antimony can be exemplified.

As the non-nucleophilic anions represented by Z⁻, an aliphatic sulfonate anion in which the α-position of the sulfonic acid is substituted with a fluorine atom, an aromatic sulfonate anion substituted with a fluorine atom or a group having a fluorine atom, a bis(alkylsulfonyl)imide anion in which the alkyl group is substituted with a fluorine atom, and a tris(alkylsulfonyl)methide anion in which the alkyl group is substituted with a fluorine atom are preferred. Especially preferred non-nucleophilic anions are an aliphatic perfluoro-sulfonate anion having from 4 to 8 carbon atoms, and a benzenesulfonate anion having a fluorine atom, and still more preferred non-nucleophilic anions are a nonafluorobutane-sulfonate anion, a perfluorooctanesulfonate anion, a pentafluorobenzenesulfonate anion, and a 3,5-bis(trifluoro-methyl)benzenesulfonate anion.

As the examples of the organic groups represented by R₂₀₁, R₂₀₂ and R₂₀₃, the corresponding groups in the later-described compounds represented by formula (ZI-1), (ZI-2) or (ZI-3) can be exemplified.

The compound represented by formula (ZI) may be a compound having a plurality of structures represented by formula (ZI). For instance, compound (ZI) may be a compound having a structure that at least one of R₂₀₁, R₂₀₂ and R₂₀₃ of the compound represented by formula (ZI) is bonded to at least one of R₂₀₁, R₂₀₂ and R₂₀₃ of another compound represented by formula (ZI).

The following compounds (ZI-1), (ZI-2) and (ZI-3) can be exemplified as more preferred components (ZI).

Compound (ZI-1) is an arylsulfonium compound that at least one of R₂₀₁, to R₂₀₃ in formula (ZI) represents an aryl group, i.e., a compound having arylsulfonium as a cation.

All of R₂₀₁ to R₂₀₃ of the arylsulfonium compound may be aryl groups, or a part of R₂₀₁ to R₂₀₃ may be an aryl group and the remainder may be an alkyl group or a cycloalkyl group.

As the arylsulfonium compounds, e.g., a triarylsulfonium compound, a diarylalkylsulfonium compound, an aryldialkyl-sulfonium compound, a diarylcycloalkylsulfonium compound, and an aryldicycloalkylsulfonium compound are exemplified.

As the aryl groups of the arylsulfonium compound, a phenyl group and a naphthyl group are preferred, and the more preferred group is a phenyl group. The aryl group may be an aryl group having a heterocyclic structure having an oxygen atom, a nitrogen atom or a sulfur atom. As the aryl group having a heterocyclic structure, e.g., a pyrrole residue (a group formed by eliminating one hydrogen atom from pyrrole), a furan residue (a group formed by eliminating one hydrogen atom from furan), a thiophene residue (a group formed by eliminating one hydrogen atom from thiophene), an indole residue (a group formed by eliminating one hydrogen atom from indole), a benzofuran residue (a group formed by eliminating one hydrogen atom from benzofuran), and a benzothiophene residue (a group formed by eliminating one hydrogen atom from benzothiophene) can be exemplified. When the arylsulfonium compound has two or more aryl groups, these two or more aryl groups may be the same or different.

As an alkyl group or a cycloalkyl group that the arylsulfonium compound has according to necessity, a straight chain or branched alkyl group having from 1 to 15 carbon atoms and a cycloalkyl group having from 3 to 15 carbon atoms are preferred, e.g., a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, a t-butyl group, a cyclopropyl group, a cyclobutyl group and a cyclohexyl group can be exemplified.

The aryl group, alkyl group and cycloalkyl group represented by R₂₀₁, R₂₀₂ and R₂₀₃ may have a substituent and, e.g., an alkyl group (e.g., having from 1 to 15 carbon atoms), a cycloalkyl group (e.g., having from 3 to 15 carbon atoms), an aryl group (e.g., having from 6 to 14 carbon atoms), an alkoxyl group (e.g., having from 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, and a phenylthio group are exemplified as the substituents. The preferred substituents are a straight chain or branched alkyl group having from 1 to 12 carbon atoms, a cycloalkyl group having from 3 to 12 carbon atoms, and a straight chain, branched or cyclic alkoxyl group having from 1 to 12 carbon atoms, and the most preferred substituents are an alkyl group having from 1 to 4 carbon atoms and an alkoxyl group having from 1 to 4 carbon atoms. The substituent may be substituted on any one of three of R₂₀₁ to R₂₀₃, or may be substituted on all of the three. When R₂₀₁, R₂₀₂ and R₂₀₃ each independently represents an aryl group, it is preferred that the substituent be substituted on the p-position of the aryl group.

Compound (ZI-2) is described below.

Compound (ZI-2) is a compound in the case where R₂₀₁, R₂₀₂ and R₂₀₃ in formula (ZI) each independently represents an organic group not containing an aromatic ring. The aromatic ring also includes an aromatic ring containing a hetero atom.

The organic groups not containing an aromatic ring represented by R₂₀₁ to R₂₀₃ generally have from 1 to 30 carbon atoms, and preferably from 1 to 20 carbon atoms.

R₂₀₁, R₂₀₂ and R₂₀₃ each preferably represents an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group, more preferably a straight chain or branched 2-oxoalkyl group, a 2-oxocycloalkyl group or an alkoxycarbonylmethyl group, and especially preferably a straight or branched 2-oxoalkyl group.

The alkyl group and cycloalkyl group represented by R₂₀₁ to R₂₀₃ are preferably a straight chain or branched alkyl group having from 1 to 10 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group), and a cycloalkyl group having from 3 to 10 carbon atoms (e.g., a cyclopentyl group, a cyclohexyl group, a norbonyl group). The alkyl group is more preferably a 2-oxoalkyl group or an alkoxycarbonylmethyl group. The cycloalkyl group is more preferably a 2-oxocycloalkyl group.

The 2-oxoalkyl group may be either a straight chain or branched group, and a group having >C═O on the 2-position of the above alkyl group can be exemplified as a preferred group.

The 2-oxocycloalkyl group is preferably a group having >C═O on the 2-position of the above cycloalkyl group.

As the alkoxyl group in the alkoxycarbonylmethyl group, an alkoxyl group preferably having from 1 to 5 carbon atoms (e.g., a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group) can be exemplified.

R₂₀₁ to R₂₀₃ may further be substituted with a halogen atom, an alkoxyl group (e.g., having from 1 to 5 carbon atoms), a hydroxyl group, a cyano group, or a nitro group.

Compound (ZI-3) is a compound represented by the following formula (ZI-3), which compound has a phenacyl-sulfonium salt structure.

In formula (ZI-3), R_(1c), R_(2c), R_(3c), R_(4c) and R_(5c) each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkoxy group, or a halogen atom.

R_(6c) and R_(7c) each independently represents a hydrogen atom, an alkyl group or a cycloalkyl group.

R_(x) and R_(y) each independently represents an alkyl group, a cycloalkyl group, an allyl group, or a vinyl group.

Any two or more of R_(1c) to R_(5c), R_(6c) and R_(7c), and R_(x) and R_(y) may be bonded to each other to form cyclic structures, respectively, and the cyclic structures may contain an oxygen atom, a sulfur atom, an ester bond, or an amido bond. As the groups formed by any two or more of R_(1c) to R_(5c), R_(6c) and R_(7c), and R_(x) and R_(y), a butylene group, a pentylene group, etc., can be exemplified.

Z_(c) ⁻ represents a non-nucleophilic anion, and the same non-nucleophilic anions as represented by X⁻ in formula (ZI) can be exemplified.

The alkyl groups represented by R_(1c) to R_(7c) may be either straight chain or branched, e.g., an alkyl group having from 1 to 20 carbon atoms, preferably a straight chain or branched alkyl group having from 1 to 12 carbon atoms (e.g., a methyl group, an ethyl group, a straight chain or branched propyl group, a straight chain or branched butyl group, a straight chain or branched pentyl group) can be exemplified. As the cycloalkyl groups represented by R_(1c) to R_(7c), a cycloalkyl group having from 3 to 8 carbon atoms (e.g., a cyclopentyl group and a cyclohexyl group) can be exemplified.

The alkoxyl groups represented by R_(1c) to R_(5c) may be any of straight chain, branched and cyclic, e.g., an alkoxyl group having from 1 to 10 carbon atoms, preferably a straight chain or branched alkoxyl group having from 1 to 5 carbon atoms (e.g., a methoxy group, an ethoxy group, a straight chain or branched propoxy group, a straight chain or branched butoxy group, a straight chain or branched pentoxy group), a cyclic alkoxyl group having from 3 to 8 carbon atoms (e.g., a cyclopentyloxy group, a cyclohexyloxy group) can be exemplified.

It is preferred that any of R_(1c) to R_(5c) represents a straight chain or branched alkyl group, a cycloalkyl group, or a straight chain, branched or cyclic alkoxyl group, it is more preferred that the sum total of the carbon atoms of R_(1c) to R_(5c) is from 2 to 15, by which the solubility in a solvent increases and generation of particles during preservation can be restrained.

As the alkyl group and cycloalkyl group represented by R_(x) and R_(y), the same alkyl groups and cycloalkyl groups represented by R_(1c) to R_(7c) can be exemplified, and a 2-oxoalkyl group, a 2-oxocycloalkyl group and an alkoxycarbonylmethyl group are more preferred.

As the 2-oxoalkyl group and the 2-oxocycloalkyl group, groups having >C═O on the 2-position of the alkyl group and the cycloalkyl group represented by R_(1c) to R_(7c) can be exemplified.

As the alkoxyl group of the alkoxycarbonylmethyl group, the same alkoxyl groups as those represented by R_(1c) and R_(5c), can be exemplified.

R_(x) and R_(y) each preferably represents an alkyl group or a cycloalkyl group having 4 or more carbon atoms, more preferably 6 or more carbon atoms, and still more preferably an alkyl group or a cycloalkyl group having 8 or more carbon atoms.

In formulae (ZII) and (ZIII), R₂₀₄, R₂₀₅, R₂₀₆ and R₂₀₇ each independently represents an aryl group, an alkyl group or a cycloalkyl group.

The aryl group represented by R₂₀₄ to R₂₀₇ is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group. The aryl group represented by R₂₀₄ to R₂₀₇ may be an aryl group having a heterocyclic structure having an oxygen atom, a nitrogen atom or a sulfur atom. As the aryl group having a heterocyclic structure, e.g., a pyrrole residue (a group formed by eliminating one hydrogen atom from pyrrole), a furan residue (a group formed by eliminating one hydrogen atom from furan), a thiophene residue (a group formed by eliminating one hydrogen atom from thiophene), an indole residue (a group formed by eliminating one hydrogen atom from indole), a benzofuran residue (a group formed by eliminating one hydrogen atom from benzofuran), and a benzothiophene residue (a group formed by eliminating one hydrogen atom from benzothiophene) can be exemplified.

The alkyl group and the cycloalkyl group represented by R₂₀₄ to R₂₀₇ are preferably a straight chain or branched alkyl group having from 1 to 10 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group), and a cycloalkyl group having from 3 to 10 carbon atoms (e.g., a cyclopentyl group, a cyclohexyl group, a norbonyl group).

The aryl group, alkyl group and cycloalkyl group represented by R₂₀₄ to R₂₀₇ may have a substituent. As the substituents that the aryl group, alkyl group and cycloalkyl group represented by R₂₀₄ to R₂₀₇ may have, e.g., an alkyl group (e.g., having from 1 to 15 carbon atoms), a cycloalkyl group (e.g., having from 3 to 15 carbon atoms), an aryl group (e.g., having from 6 to 15 carbon atoms), an alkoxyl group (e.g., having from 1 to 15 carbon atoms), a halogen atom, a hydroxyl group, and a phenylthio group can be exemplified.

Z⁻ represents a non-nucleophilic anion, and the same non-nucleophilic anions as those represented by Z⁻ in formula (ZI) can be exemplified.

As the acid generators usable in combination, the compounds represented by the following formula (ZIV), (ZV) or (ZVI) can further be exemplified.

In formulae (ZIV), (ZV) and (ZVI), Ar₃ and Ar₄ each independently represents an aryl group.

R₂₀₆, R₂₀₇ and R₂₀₈ each independently represents an alkyl group, a cycloalkyl group or an aryl group.

A represents an alkylene group, an alkenylene group or an arylene group.

Of the acid generators usable in combination, more preferred compounds are the compounds represented by formulae (ZI), (ZII) and (ZIII).

Further, as the acid generators usable in combination, a compound generating an acid having one sulfonic acid group or an imido group is preferred, a compound generating a monovalent perfluoroalkanesulfonic acid, a compound generating an aromatic sulfonic acid substituted with a monovalent fluorine atom or a group containing a fluorine atom, and a compound generating an imidic acid substituted with a monovalent fluorine atom or a group containing a fluorine atom are more preferred, and a sulfonium salt of a fluorine-substituted alkanesulfonic acid, a fluorine-substituted benzenesulfonic acid, or a fluorine-substituted imidic acid is still more preferred. As the acid generators usable in combination, a fluorine-substituted alkanesulfonic acid, a fluorine-substituted benzenesulfonic acid, and fluorine-substituted imidic acid each having pKa of −1 or less of generated acid are especially preferred, by which sensitivity is improved.

The examples of especially preferred acid generators usable in combination are shown below.

The acid generators usable in combination can be used alone, or two or more in combination.

The content of the acid generators usable in combination in a photosensitive composition is preferably from 0.1 to 20 mass % based on the total solids content of the photosensitive composition, more preferably from 0.5 to 10 mass %, and still more preferably from 1 to 7 mass %.

[3] (C) A resin capable of decomposing by the action of an acid to increase solubility in an alkali developing solution (referred to as also component (C)):

A resin capable of decomposing by the action of an acid to increase solubility in an alkali developing solution for use in the positive photosensitive composition in the invention is a resin having a group decomposable by the action of an acid (hereinafter referred to as “an acid-decomposable group”) on the main chain or side chain of the resin, or on both the main chain and side chain. A resin having a group decomposable by the action of an acid on the side chain is more preferred.

A preferred acid-decomposable group is a group obtained by substituting the hydrogen atom of a —COOH group or an —OH group with a group capable of being desorbed by an acid.

An especially preferred acid-decomposable group in the invention is an acetal group or a tertiary ester group.

The parent resin in the case where the acid-decomposable group is bonded as the side chain is an alkali-soluble resin having an —OH group or a —COOH group on the side chain. For example, the later-described alkali-soluble resins can be exemplified.

The alkali dissolution rate of these alkali-soluble resins is preferably 170 Å/sec or more when measured using 0.261N tetramethylammonium hydroxide (TMAH) at 23° C., especially preferably 330 Å/sec or more.

From this point of view, particularly preferred alkali-soluble resins are o-, m-, p-poly(hydroxystyrene) and copolymers thereof, hydrogenated poly(hydroxystyrene), halogen- or alkyl-substituted poly(hydroxystyrene), a partially O-alkylated or O-acylated product of poly-(hydroxystyrene), styrene-hydroxystyrene copolymers, α-methylstyrene-hydroxystyrene copolymers, alkali-soluble resins having a hydroxystyrene structure unit such as hydrogenated novolak resins, (meth)acrylic acid, and alkali-soluble resins containing a repeating unit having a carboxyl group such as norbornenecarboxylic acid.

As repeating units having a preferred acid-decomposable group, e.g., t-butoxycarbonyloxystyrene, 1-alkoxyethoxy-styrene, and (meth)acrylic acid tertiary alkyl ester are exemplified, and 2-alkyl-2-adamantyl(meth)acrylate and dialkyl(1-adamantyl)methyl(meth)acrylate are more preferred.

Components (C) for use in the invention can be obtained, as disclosed in EP 254853, JP-A-2-25850, JP-A-3-223860 and JP-A-4-251259, by reacting an alkali-soluble resin with the precursor of an acid-decomposable group, or copolymerizing an alkali-soluble resin monomer to which an acid-decomposable group is bonded with various monomers.

When the positive photosensitive composition of the invention is irradiated with KrF excimer laser beams, electron beams, X-rays, or high energy rays of wavelength of 50 nm or lower (e.g., EUV), it is preferred for a resin of component (C) to have a hydroxystyrene repeating unit, more preferably a copolymer of hydroxystyrene/hydroxystyrene protected with an acid-decomposable group, or hydroxystyrene/(meth)acrylic acid tertiary alkyl ester.

The specific examples of component (C) for use in the invention are shown below, but the invention is not restricted thereto.

In the above specific examples, tBu means a t-butyl group.

The content of an acid-decomposable group is expressed by B/(B+S), taking the number of the acid-decomposable groups in a resin as (B), and the number of alkali-soluble groups not protected with acid-eliminable groups as (S). The content is preferably from 0.01 to 0.7, more preferably from 0.05 to 0.50, and still more preferably from 0.05 to 0.40.

When the positive photosensitive composition in the invention is irradiated with ArF excimer laser beams, it is preferred that the resin of component (C) is a resin having a monocyclic or polycyclic alicyclic hydrocarbon structure and capable of decomposing by the action of an acid to thereby increase the solubility in an alkali developing solution.

As a resin having a monocyclic or polycyclic alicyclic hydrocarbon structure and capable of decomposing by the action of an acid to thereby increase the solubility in an alkali developing solution (hereinafter also referred to as “an alicyclic hydrocarbon acid-decomposable resin”), a resin containing at least one repeating unit selected from the group consisting of a repeating unit having a partial structure containing alicyclic hydrocarbon represented by any of the following formulae (pI) to (pV), and a repeating unit represented by the following formula (II-AB) is preferred.

In formulae (pI) to (pV), R₁₁ represents a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, or a sec-butyl group; and Z represents an atomic group necessary to form a cycloalkyl group together with a carbon atom.

R₁₂, R₁₃, R₁₄, R₁₅ and R₁₆ each independently represents a straight chain or branched alkyl group, or a cycloalkyl group, provided that at least one of R₁₂ to R₁₄, or either R₁₅ or R₁₆ represents a cycloalkyl group.

R₁₇, R₁₈, R₁₉, R₂₀ and R₂₁, each independently represents a hydrogen atom, a straight chain or branched alkyl group or a cycloalkyl group, provided that at least one of R₁₇ to R₂₁, represents a cycloalkyl group, and either R₁₉ or R₂₁, represents a straight chain or branched alkyl group or a cycloalkyl group.

R₂₂, R₂₃, R₂₄ and R₂₅ each independently represents a hydrogen atom, a straight chain or branched alkyl group or a cycloalkyl group, provided that at least one of R₂₂ to R₂₅ represents a cycloalkyl group, and R₂₃ and R₂₄ may be bonded to each other to form a ring.

In formula (II-AB), R₁₁′ and R₁₂′ each independently represents a hydrogen atom, a cyano group, a halogen atom, or an alkyl group.

Z′ contains bonded two carbon atoms (C—C) and represents an atomic group to form an alicyclic structure.

Formula (II-AB) is more preferably represented by the following formula (II-AB1) or (II-AB2).

In formulae (II-AB1) and (II-AB2), R₁₃′, R₁₄′, R₁₅′ and R₁₆′ each independently represents a hydrogen atom, a halogen atom, a cyano group, —COOH, —COOR₅, a group decomposable by the action of an acid, —C(═O)—X-A′-R₁₇′, an alkyl group, or a cycloalkyl group. At least two of R₁₃′ to R₁₆′ may be bonded to form a ring.

R₅ represents an alkyl group, a cycloalkyl group, or a group having a lactone structure.

X represents an oxygen atom, a sulfur atom, —NH—, —NHSO₂— or —NHSO₂NH—.

A′ represents a single bond or a divalent linking group.

R₁₇′ represents —COOH, —COOR₅, —CN, a hydroxyl group, an alkoxyl group, —CO—NH—R₆, —CO—NH—SO₂—R₆, or a group having a lactone structure.

R₆ represents an alkyl group or a cycloalkyl group.

n represents 0 or 1.

The alkyl group represented by R₁₂ to R₂₅ in formulae (pI) to (pV) is preferably a straight chain or branched alkyl group having from 1 to 4 carbon atoms, e.g., a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a sec-butyl group are exemplified.

The cycloalkyl groups represented by R₁₂ to R₂₅ or the cycloalkyl group formed by Z and carbon atoms may be monocyclic or polycyclic. Specifically, groups having a monocyclic, bicyclic, tricyclic or tetracyclic structure having 5 or more carbon atoms can be exemplified. The number of carbon atoms of the groups is preferably from 6 to 30, and particularly preferably from 7 to 25.

As preferred cycloalkyl groups, an adamantyl group, a noradamantyl group, a decalin residue, a tricyclodecanyl group, a tetracyclododecanyl group, a norbornyl group, a cedrol group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclodecanyl group, and a cyclododecanyl group can be exemplified. More preferred cycloalkyl groups are an adamantyl group, a norbornyl group, a cyclohexyl group, a cyclopentyl group, a tetracyclododecanyl group, and a tricyclodecanyl group.

These alkyl groups and cycloalkyl groups may have further substituents. As further substituents of these alkyl groups and cycloalkyl groups, an alkyl group (having from 1 to 4 carbon atoms), a halogen atom, a hydroxyl group, an alkoxyl group (having from 1 to 4 carbon atoms), a carboxyl group, and an alkoxycarbonyl group (having from 2 to 6 carbon atoms) can be exemplified. As substituents that these alkyl group, alkoxyl group and alkoxycarbonyl group may further have, a hydroxyl group, a halogen atom and an alkoxyl group can be exemplified.

The structures represented by formulae (pI) to (pV) in the resin can be used for the protection of alkali-soluble groups. As the alkali-soluble groups, various groups well known in this technical field can be exemplified.

Specifically, the structures in which the hydrogen atoms of carboxylic acid group, a sulfonic acid group, a phenol group and a thiol group are substituted with the structures represented by formulae (pI) to (pV) are exemplified, and preferably the structures in which the hydrogen atoms of carboxylic acid group and a sulfonic acid group are substituted with the structures represented by formulae (pI) to (pV) are exemplified.

As the repeating unit having the alkali-soluble group protected with the structure represented by any of the above formulae (pI) to (pV), a repeating unit represented by the following formula (pA) is preferred.

In formula (pA), R represents a hydrogen atom, a halogen atom, or a straight chain or branched alkyl group having from 1 to 4 carbon atoms, and a plurality of R's may be the same or different.

A represents a single group or the combination of two or more groups selected from the group consisting of a single bond, an alkylene group, an ether group, a thioether group, a carbonyl group, an ester group, an amido group, a sulfonamido group, a urethane group, and a urea group. A single bond is preferred.

R_(p1) represents a group represented by any of formulae (pI) to (pVI).

The repeating unit represented by (pA) is most preferably a repeating unit by 2-alkyl-2-adamantyl (meth)acrylate and dialkyl(1-adamantyl)methyl (meth)acrylate.

The specific examples of the repeating units represented by formula (pA) are shown below, but the invention is not restricted thereto.

(In the formulae, R_(x) represents H, CH₃, CF₃, CH₂OH, Rxa, and Rxb each independently represents an alkyl group having from 1 to 4 carbon atoms.)

As the halogen atoms represented by R₁₁′ and R₁₂′ in formula (II-AB), a chlorine atom, a bromine atom, a fluorine atom and an iodine atom are exemplified.

As the alkyl groups represented by R₁₁′ and R₁₂′, straight chain or branched alkyl groups having from 1 to 10 carbon atoms are exemplified.

The atomic group represented by Z′ to form an alicyclic structure is an atomic group to form a repeating unit having an alicyclic hydrocarbon structure, which may have a substituent, and an atomic group to form a repeating unit having a bridged alicyclic hydrocarbon structure is preferred above all.

As the skeleton of alicyclic hydrocarbon formed, the same alicyclic hydrocarbon groups as represented by R₁₂ to R₂₅ in formulae (pI) to (pV) are exemplified.

The skeleton of the alicyclic hydrocarbon structure may have a substituent, and as the substituents, the groups represented by R₁₃′ to R₁₆′ in formula (II-AB1) or (II-AB2) can be exemplified.

In the alicyclic hydrocarbon-based acid-decomposable resin in the invention, a group capable of decomposing by the action of an acid can be contained in at least one repeating unit of a repeating unit having a partial structure containing alicyclic hydrocarbon represented by any of formulae (pI) to (pV), a repeating unit represented by formula (II-AB), and a repeating unit of the later-described copolymer component.

Various substituents of R₁₃′ to R₁₆′ in formula (II-AB1) or (II-AB2) can also be used as the substituents of the atomic group to form an alicyclic hydrocarbon structure in formula (II-AB), or atomic group Z to form a bridged alicyclic hydrocarbon structure.

The specific examples of the repeating units represented by formula (II-AB1) or (II-AB2) are shown below, but the invention is not restricted thereto.

The alicyclic hydrocarbon-based acid-decomposable resin in the invention preferably contains a repeating unit having a group having a lactone structure. As the group having a lactone structure, any group having a lactone structure can be used, but preferably groups having 5- to 7-membered ring lactone structures, and 5- to 7-membered ring lactone structures condensed with other ring structures in the form of forming a bicyclo structure or a spiro structure are preferred. As the group having a lactone structure, a group having a lactone structure represented by any of the following formulae (LC1-1) to (LC1-16) is more preferred. A group having a lactone structure may be directly bonded to the main chain of a repeating unit. Preferred lactone structures are (LC1-1), (LC1-4) (LC1-5), (LC1-6), (LC1-13) and (LC1-14). By the use of a specific lactone structure, line edge roughness and development defect are bettered.

A lactone structure moiety may have or may not have a substituent (Rb₂). As preferred substituent (Rb₂), an alkyl group having from 1 to 8 carbon atoms, a cycloalkyl group having from 3 to 7 carbon atoms, an alkoxyl group having from 1 to 8 carbon atoms, an alkoxycarbonyl group having from 1 to 8 carbon atoms, a carboxyl group, a halogen atom, a hydroxyl group, a cyano group, and an acid-decomposable group are exemplified. n₂ represents an integer of from 0 to 4. When n₂ is 2 or more, a plurality of Rb₂ may be the same or different, and a plurality of Rb₂ may be bonded to each other to form a ring.

As the repeating units having a group having a lactone structure represented by any of formulae (LC1-1) to (LC1-16), a repeating unit in which at least one of R₁₃′ to R₁₆′ in formula (II-AB1) or (II-AB2) is a group having a lactone structure represented by any of formulae (LC1-1) to (LC1-16) (for example, R₅ of —COOR₅ is a group having a lactone structure represented by any of formulae (LC1-1) to (LC1-16)), or a repeating unit represented by the following formula (AI) can be exemplified.

In formula (AI), Rb₀ represents a hydrogen atom, a halogen atom, or an alkyl group having from 1 to 4 carbon atoms. As the preferred substituents that the alkyl group represented by Rb₀ may have, a hydroxyl group and a halogen atom are exemplified.

As the halogen atom represented by Rb₀, a fluorine atom, a chlorine atom, a bromine atom and an iodine atom can be exemplified.

Rb₀ preferably represents a hydrogen atom or a methyl group.

Ab represents a single bond, an alkylene group, a divalent linking group having a monocyclic or polycyclic alicyclic hydrocarbon structure, an ether group, an ester group, a carbonyl group, a carboxyl group, or a divalent linking group combining these groups.

Ab preferably represents a single bond or a linking group represented by -Ab₁-CO₂—. Ab₁ represents a straight chain or branched alkylene group, or a monocyclic or polycyclic cycloalkylene group, and preferably a methylene group, an ethylene group, a cyclohexyl group, an adamantyl group, or a norbornyl group.

V represents a group having a lactone structure represented by any of formulae (LC1-1) to (LC1-16).

Repeating units having a lactone structure generally have optical isomers, and any optical isomer may be used. One kind of optical isomer may be used alone, or a plurality of optical isomers may be used as mixture. When one kind of optical isomer is mainly used, the optical purity (ee) of the optical isomer is preferably 90 or more, and more preferably 95 or more.

The specific examples of repeating units having a group having a lactone structure are shown below, but the invention is not limited thereto.

(In the formulae, Rx represents H, CH₃, CH₂OH or CF₃.)

(In the formulae, Rx represents H, CH₃, CH₂OH or CF₃.)

(In the formulae, Rx represents H, CH₃, CH₂OH or CF₃.)

It is preferred for the alicyclic hydrocarbon-based acid-decomposable resin of the invention to have a repeating unit having a group having an alicyclic hydrocarbon structure substituted with a polar group, by which adhesion with a substrate and affinity with a developing solution are improved. As the alicyclic hydrocarbon structure of the alicyclic hydrocarbon structure substituted with a polar group, an adamantyl group, a diamantyl group, and a norbornane group are preferred. As the polar group, a hydroxyl group and a cyano group are preferred. As the group having the alicyclic hydrocarbon structure substituted with a polar group, a group represented by any of the following formulae (VIIa) to (VIId) is preferred.

In formula (VIIa) to (VIIc), R_(2c), R_(3c) and R_(4c) each independently represents a hydrogen atom, a hydroxyl group, or a cyano group, provided that at least one of R_(2c), R_(3c) and R_(4c) represents a hydroxyl group or a cyano group. Preferably one or two of R_(2c), R_(3c) and R_(4c) represent a hydroxyl group and the remainder represent a hydrogen atom. In formula (VIIa), more preferably two of R_(2c), R_(3c) and R_(4c) represent a hydroxyl group and the remainder represents a hydrogen atom.

As the repeating unit having a group represented by any of formulae (VIIa) to (VIId), a repeating unit in which at least one of R₁₃′ to R₁₆′ in formula (II-AB1) or (II-AB2) is a group represented by any of formulae (VIIa) to (VIId) (for example, R₅ of —COOR₅ is a group represented by any of formulae (VIIa) to (VIId),), or a repeating unit represented by any of the following formulae (AIIa) to (AIId) can be exemplified.

In formulae (AIIa) to (AIId),), R_(1c) represents a hydrogen atom, a methyl group, a trifluoromethyl group, or a hydroxymethyl group.

The specific examples of the repeating units represented by formulae (AIIa) to (AIId) are shown below, but the invention is not restricted thereto.

The alicyclic hydrocarbon-based acid-decomposable resin in the invention may have a repeating unit represented by the following formula (VIII).

In formula (VIII), Z₂ represents —O— or —N(R₄₁)—. R₄₁ represents a hydrogen atom, a hydroxyl group, an alkyl group, or —OSO₂—R₄₂. R₄₂ represents an alkyl group, a cycloalkyl group, or a camphor residue. The alkyl group represented by R₄₁ and R₄₂ may be substituted with a halogen atom (preferably a fluorine atom) and the like.

As the specific examples of the repeating units represented by formula (VIII), the following compounds are exemplified, but the invention is not restricted thereto.

It is preferred for the alicyclic hydrocarbon-based acid-decomposable resin in the invention to have a repeating unit having an alkali-soluble group, and it is more preferred to have a repeating unit having a carboxyl group, by which the resolution in the use for contact hole is enhanced. As the repeating units having a carboxyl group, a repeating unit having a carboxyl group directly bonded to the main chain of a resin such as a repeating unit by acrylic acid or methacrylic acid, a repeating unit having a carboxyl group bonded to the main chain of a resin via a linking group, and a repeating unit having a carboxyl group introduced to the terminals of a polymer chain by polymerization with a polymerization initiator having an alkali-soluble group and a chain transfer agent are exemplified, and any of these repeating units is preferably used. Linking groups may have a monocyclic or polycyclic hydrocarbon structure. The repeating unit by acrylic acid or methacrylic acid is especially preferred.

The alicyclic hydrocarbon-based acid-decomposable resin in the invention may further have a repeating unit having one to three groups represented by the following formula (F1), by which line edge roughness property is improved.

In formula (F1), R₅₀, R₅₁, R₅₂, R₅₃, R₅₄ and R₅₅ each independently represents a hydrogen atom, a fluorine atom, or an alkyl group, provided that at least one of R₅₀ to R₅₅ represents a fluorine atom, or an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom.

Rxa represents a hydrogen atom or an organic group (preferably an acid-decomposable protective group, an alkyl group, a cycloalkyl group, an acyl group, or an alkoxycarbonyl group).

The alkyl group represented by R₅₀ to R₅₅ may be substituted with a halogen atom, e.g., a fluorine atom, or a cyano group, and preferably an alkyl group having from 1 to 3 carbon atoms, e.g., a methyl group and a trifluoromethyl group can be exemplified.

It is preferred that all of R₅₀ to R₅₅ represent a fluorine atom.

As the organic group represented by Rxa, an acid-decomposable protective group, and an alkyl group, a cycloalkyl group, an acyl group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkoxycarbonylmethyl group, an alkoxymethyl group, and a 1-alkoxyethyl group, each of which may have a substituent, are preferred.

The repeating unit having the group represented by formula (F1) is preferably a repeating unit represented by the following formula (F2).

In formula (F2), Rx represents a hydrogen atom, a halogen atom, or an alkyl group having from 1 to 4 carbon atoms. As preferred substituents that the alkyl group represented by Rx may have, a hydroxyl group and a halogen atom are exemplified.

Fa represents a single bond or a straight chain or branched alkylene group, and preferably a single bond.

Fb represents a monocyclic or polycyclic hydrocarbon group.

Fc represents a single bond or a straight chain or branched alkylene group, and preferably a single bond or a methylene group.

F₁ represents a group represented by formula (F1).

P₁ is from 1 to 3.

As the cyclic hydrocarbon group represented by Fb, a cyclopentyl group, a cyclohexyl group, or a norbornyl group is preferred.

The specific examples of the repeating units having the group represented by formula (F1) are shown below, but the invention is not restricted thereto.

The alicyclic hydrocarbon-based acid-decomposable resin in the invention may further contain a repeating unit having an alicyclic hydrocarbon structure and not showing acid decomposability, by containing such a repeating unit, the elution of low molecular weight components from a resist film into an immersion liquid can be reduced at the time of immersion exposure. As such repeating units, e.g., 1-adamantyl(meth)acrylate, tricyclodecanyl(meth)acrylate, and cyclohexyl(meth)acrylate, are exemplified.

The alicyclic hydrocarbon-based acid-decomposable resin in the invention can contain various kinds of repeating structural units, besides the above repeating structural units, for the purpose of the adjustments of dry etching resistance, aptitude for standard developing solutions, adhesion to a substrate, resist profile, and further, general requisite characteristics of resists, e.g., resolution, heat resistance and sensitivity.

As these repeating structural units, the repeating structural units corresponding to the monomers shown below can be exemplified, but the invention is not restricted thereto.

By containing such various repeating structural units, fine adjustment of performances required of the alicyclic hydrocarbon-based acid-decomposable resin, in particular the following performances, becomes possible, that is,

(1) Solubility in a coating solvent, (2) A film-forming property (a glass transition point), (3) Alkali developability, (4) Decrease of layer thickness (hydrophobic-hydrophilic property, selection of an alkali-soluble group), (5) Adhesion of an unexposed area to a substrate, and (6) Dry etching resistance.

The examples of such monomers include compounds having one addition polymerizable unsaturated bond selected from acrylic esters, methacrylic esters, acrylamides, methacryl-amides, allyl compounds, vinyl ethers, vinyl esters, etc.

In addition to the aforementioned compounds, addition polymerizable unsaturated compounds copolymerizable with the monomers corresponding to the above various repeating structural units may be used for copolymerization.

In the alicyclic hydrocarbon-based acid-decomposable resin, the molar ratio of the content of each repeating structural unit is arbitrarily set to adjust dry etching resistance and aptitude for standard developing solutions of a resist, adhesion to a substrate, and resist profile, in addition, general requisite characteristics of a resist, e.g., resolution, heat resistance and sensitivity.

As preferred embodiments of the alicyclic hydrocarbon-based acid-decomposable resin in the invention, the following resins are exemplified.

(1) A resin containing a repeating unit having a partial structure containing the alicyclic hydrocarbon represented by any of formulae (pI) to (pV) (a side chain type), preferably a resin containing a (meth)acrylate repeating unit having the structure of any of formulae (pI) to (pV);

(2) A resin containing a repeating unit represented by formula (II-AB) (a main chain type); however, the following is further exemplified as embodiment (2): (3) A resin containing a repeating unit represented by formula (II-AB), a maleic anhydride derivative and a (meth)acrylate structure (a hybrid type).

In the alicyclic hydrocarbon-based acid-decomposable resin, the content of a repeating unit having an acid-decomposable group is preferably from 10 to 60 mol % in the total repeating structural units, more preferably from 20 to 50 mol %, and still more preferably from 25 to 40 mol %.

In the alicyclic hydrocarbon-based acid-decomposable resin, the content of a repeating unit having a partial structure containing the alicyclic hydrocarbon represented by any of formulae (pI) to (pV) is preferably from 20 to 70 mol % in the total repeating structural units, more preferably from 20 to 50 mol %, and still more preferably from 25 to 40 mol %.

In the alicyclic hydrocarbon-based acid-decomposable resin, the content of a repeating unit represented by formula (II-AB) is preferably from 10 to 60 mol % in the total repeating structural units, more preferably from 15 to 55 mol %, and still more preferably from 20 to 50 mol %.

The content of the repeating structural units on the basis of the monomers of further copolymerization components in the resin can also be optionally set according to the desired resist performances, and the content is generally preferably 99 mol % or less to the total mol number of the repeating structural units having a partial structure containing the alicyclic hydrocarbon represented by any of formulae (pI) to (pV) and the repeating units represented by formula (II-AB), more preferably 90 mol % or less, and still more preferably 80 mol % or less.

When the composition in the invention is for ArF exposure, it is preferred that the resin does not have an aromatic group from the aspect of the transparency to ArF rays.

The alicyclic hydrocarbon-based acid-decomposable resin for use in the invention is preferably such that all the repeating units consist of (meth)acrylate repeating units. In this case, any of the following cases can be used, that is, a case where all the repeating units consist of methacrylate, a case where all the repeating units consist of acrylate, and a case where the repeating units consist of mixture of methacrylate and acrylate, but it is preferred that acrylate repeating units account for 50 mol % or less of all the repeating units. More preferred resins are ternary copolymers comprising from 20 to 50 mol % of repeating units having a partial structure containing the alicyclic hydrocarbon represented by any of formulae (pI) to (pV), from 20 to 50 mol % of repeating units having a lactone structure, and from 5 to 30 mol % of repeating units having an alicyclic hydrocarbon structure substituted with a polar group, and quaternary copolymers further containing from 0 to 20 mol % of other repeating units.

Especially preferred resins are ternary copolymers comprising from 20 to 50 mol % of a repeating unit having an acid-decomposable group represented by any of the following formulae (ARA-1) to (ARA-5), from 20 to 50 mol % of a repeating unit having a lactone group represented by any of the following formulae (ARL-1) to (ARL-6), and from 5 to 30 mol % of a repeating unit having an alicyclic hydrocarbon structure substituted with a polar group represented by any of the following formulae (ARH-1) to (ARH-3), and quaternary copolymers further containing from 5 to 20 mol % of a repeating unit having a carboxyl group or a structure represented by formula (F1), and a repeating unit having an alicyclic hydrocarbon structure and not showing acid decomposability.

In the above formulae, Rxy₁ represents a hydrogen atom or a methyl group.

Rxa₁ and Rxb₁ each independently represents a methyl group or an ethyl group.

The alicyclic hydrocarbon-based acid-decomposable resins for use in the invention can be synthesized according to ordinary methods (e.g., radical polymerization). For instance, as ordinary methods, a batch polymerization method of dissolving a monomer and an initiator in a solvent and heating the solution to perform polymerization, and a dropping polymerization method of adding a solution of a monomer and an initiator to a heated solvent over 1 to 10 hours by dropping are exemplified, and dropping polymerization is preferred. As reaction solvents, ethers, e.g., tetrahydrofuran, 1,4-dioxane, and diisopropyl ether, ketones, e.g., methyl ethyl ketone and methyl isobutyl ketone, an ester solvent, e.g., ethyl acetate, amide solvents, e.g., dimethylformamide and dimethyacetamide, and the later-described solvents capable of dissolving the composition of the invention, e.g., propyelne glycol monomethyl ether acetate, propylene glycol monomethyl ether, and cyclohexanone are exemplified. It is more preferred to use the same solvent in polymerization as the solvent used in the resist composition in the invention, by which the generation of particles during preservation can be restrained.

It is preferred to perform polymerization reaction in the atmosphere of inert gas such as nitrogen or argon. Polymerization is initiated with commercially available radical polymerization initiators (e.g., azo initiators, peroxide and the like). As radical polymerization initiators, azo initiators are preferred, and azo initiators having an ester group, a cyano group, or a carboxyl group are preferred. As preferred initiators, azobisisobutyronitrile, azobis-dimethylvaleronitrile, dimethyl-2,2′-azibis(2-methylpropionate), etc., are exemplified. Initiators are added additionally or dividedly, if desired, and after termination of the reaction, the reaction product is put into a solvent and an objective polymer is recovered as powder or a solid state. The reaction concentration is from 5 to 50 mass %, and preferably from 10 to 30 mass %. The reaction temperature is generally from 10 to 150° C., preferably from 30 to 120° C., and more preferably from 60 to 100° C.

When the photosensitive composition according to the invention is used in the upper layer resist of a multilayer resist, it is preferred that the resin of component (C) should have a silicon atom.

As resins having a silicon atom and capable of decomposing by the action of an acid to thereby increase the solubility in an alkali developing solution, resins having a silicon atom at least on one side of the main chain and the side chain can be used. As resins having a siloxane structure on the side chain of resins, copolymer of, e.g., an olefin monomer having a silicon atom on the side chain, and a (meth)acrylic acid monomer having maleic anhydride and an acid decomposable group on the side chain.

As resins having a silicon atom, resins having a trialkylsilyl structure and a monocyclic or polycyclic siloxane structure are preferred, resins having repeating units having the structures represented by any of the following formulae (SS-1) to (SS-4) are more preferred, and (meth)acrylic ester repeating units having the structures represented by any of formulae (SS-1) to (SS-4), vinyl repeating units, and allyl repeating units are still more preferred.

In formulae (SS-1) to (SS-4), Rs represents an alkyl group having from 1 to 5 carbon atoms, preferably a methyl group or an ethyl group.

It is preferred that resins having silicon atoms have two or more kinds of different repeating units having silicon atoms, resins having both (Sa) repeating unit having from 1 to 4 silicon atoms and (Sb) repeating unit having from 5 to 10 silicon atoms are more preferred, and resins having at least one repeating unit having a structure represented by any of formulae (SS-1) to (SS-3) and a repeating unit having a structure represented by formula (SS-4) are still more preferred.

When the positive photosensitive composition of the invention is irradiated with F₂ excimer laser beams, the resin of component (C) is preferably a resin having a structure wherein the main chain and/or side chain of the polymer skeleton are substituted with fluorine atoms and capable of decomposing by the action of an acid to increase the solubility in an alkali developing solution (hereinafter also referred to as “a fluorine-based acid-decomposable resin), the resin is more preferably a resin having a hydroxyl group the 1-position of which is substituted with a fluorine atom or a fluoroalkyl group, or having a group obtained by protecting a hydroxyl group the 1-position of which is substituted with a fluorine atom or a fluoroalkyl group with an acid-decomposable group. The especially preferred resin is a resin having a hexafluoro-2-propanol structure, or a resin having a structure that the hydroxyl group of hexafluoro-2-propanol is protected with an acid-decomposable group. By the incorporation of fluorine atoms, the transparency to the far ultraviolet rays, in particular to F₂ ray (157 nm) can be improved.

As the fluorine-based acid-decomposable resin, resins having at least one repeating unit represented by any of the following formulae (FA) to (FG) are preferably exemplified.

In the above formulae, R₁₀₀, R₁₀₁, R₁₀₂ and R₁₀₃ each independently represents a hydrogen atom, a fluorine atom, an alkyl group, or an aryl group.

R₁₀₄ and R₁₀₆ each independently represents a hydrogen atom, a fluorine atom, or an alkyl group, and at least one of R₁₀₄ and R₁₀₆ represents a fluorine atom or a fluoroalkyl group. Preferably both R₁₀₄ and R₁₀₆ represent a trifluoromethyl group.

R₁₀₅ represents a hydrogen atom, an alkyl group, a cycloalkyl group, an acyl group, an alkoxycarbonyl group, or a group decomposable by the action of an acid.

A₁ represents a single bond, a divalent linking group, e.g., an alkylene group, a cycloalkylene group, an alkenylene group, an arylene group, —OCO—, —COO—, —CON(R₂₄)—, or a linking group containing a plurality of these groups. R₂₄ represents a hydrogen atom or an alkyl group.

R₁₀₇ and R₁₀₈ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxyl group, an alkoxycarbonyl group, or a group decomposable by the action of an acid.

R₁₀₉ represents a hydrogen atom, an alkyl group, a cycloalkyl group, or a group decomposable by the action of an acid.

b represents 0, 1 or 2.

Further, R₁₀₀ and R₁₀₁ in formulae (FA) and (FC) may form a ring through an alkylene group (having from 1 to 5 carbon atoms) which may be substituted with a fluorine atom.

The repeating units represented by formulae (FA) to (FG) have at least 1, preferably 3 or more, fluorine atoms per one repeating unit.

In formulae (FA) to (FG), the alkyl group is an alkyl group having from 1 to 8 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, a hexyl group, a 2-ethylhexyl group, and an octyl group are preferably exemplified.

The cycloalkyl group may be monocyclic or polycyclic. As the monocyclic cycloalkyl groups, those having from 3 to 8 carbon atoms, e.g., a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group are preferably exemplified. As the polycyclic groups, preferably those having from 6 to 20 carbon atoms, e.g., an adamantyl group, a norbornyl group, an isoboronyl group, a camphanyl group, a dicyclopentyl group, an α-pinel group, a tricyclodecanyl group, a tetracyclododecyl group, and an androstanyl group are exemplified. However, the carbon atoms in the monocyclic or polycyclic cycloalkyl groups may be substituted with hetero atoms such as an oxygen atom, etc.

The fluoroalkyl group is a fluoroalkyl group having from 1 to 12 carbon atoms, and specifically a trifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluoro-butyl group, a perfluorohexyl group, a perfluorooctyl group, a perfluorooctylethyl group, and a perfluorododecyl group are preferably exemplified.

The aryl group is an aryl group having from 6 to 15 carbon atoms, and specifically a phenyl group, a tolyl group, a dimethylphenyl group, a 2,4,6-trimethylphenyl group, a naphthyl group, an anthryl group and a 9,10-dimethoxyanthryl group are preferably exemplified.

The alkoxyl group is an alkoxyl group having from 1 to 8 carbon atoms, and specifically a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, a butoxy group, a pentoxy group, an allyloxy group, and an octoxy group are preferably exemplified.

The acyl group is an acyl group having from 1 to 10 carbon atoms, and specifically a formyl group, an acetyl group, a propanoyl group, a butanoyl group, a pivaloyl group, an octanoyl group, and a benzoyl group are preferably exemplified.

As the alkoxycarbonyl group, an i-propoxycarbonyl group, a t-butoxycarbonyl group, a t-amyloxycarbonyl group, and a 1-methyl-1-cyclohexyloxycarbonyl group, preferably a secondary, and more preferably a tertiary alkoxycarbonyl group are exemplified.

As the halogen atom, e.g., a fluorine atom, a chlorine atom, a bromine atom and an iodine atom are exemplified.

As the alkylene group, preferably an alkylene group having from 1 to 8 carbon atoms, e.g., a methylene group, an ethylene group, a propylene group, a butylene group, a hexylene group, and an octylene group are exemplified.

As the alkenylene group, preferably an alkenylene group having from 2 to 6 carbon atoms, e.g., an ethenylene group, a propenylene group and a butenylene group are exemplified.

As the cycloalkylene group, preferably a cycloalkylene group having from 5 to 8 carbon atoms, e.g., a cyclopentylene group and a cyclohexylene group are exemplified.

As the arylene group, preferably an arylene group having from 6 to 15 carbon atoms, e.g., a phenylene group, a tolylene group and a naphthylene group are exemplified.

These groups may have a substituent, and the examples of the substituents include groups having active hydrogen, e.g., an alkyl group, a cycloalkyl group, an aryl group, an amino group, an amido group, a ureido group, a urethane group, a hydroxyl group, and a carboxyl group, a halogen atom (e.g., a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom), an alkoxyl group (e.g., a methoxy group, an ethoxy group, a propoxy group, a butoxy group), a thioether group, an acyl group (e.g., an acetyl group, a propanoyl group, a benzoyl group), an acyloxy group (e.g., an acetoxy group, a propanoyloxy group, a benzoyloxy group), an alkoxycarbonyl group (e.g., a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group), a cyano group, and a nitro group are exemplified.

Here, as the alkyl, cycloalkyl and aryl groups, those described above are exemplified, but the alkyl group may further be substituted with a fluorine atom or a cycloalkyl group.

As the groups capable of decomposing by the action of an acid to increase the solubility in an alkali developing solution contained in the fluorine-based acid-decomposable resins, e.g., —O—C(R₃₆)(R₃₇)(R₃₈), —O—C(R₃₆)(R₃₇)(OR₃₉), —O—COO—C(R₃₆)(R₃₇)(R₃₈), —O—C(R₀₁)(R₀₂)COO—C(R₃₆)(R₃₇)(R₃₈), —COO—C(R₃₆)(R₃₇)(R₃₈), and —COO—C(R₃₆)(R₃₇)(OR₃₉) can be exemplified.

R₃₆, R₃₇, R₃₈ and R₃₉ each independently represents an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, or an alkenyl group; R₀₁ and R₀₂ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group (e.g., a vinyl group, an allyl group, a butenyl group, a cyclohexenyl group), an aralkyl group (e.g., a benzyl group, a phenethyl group, a naphthylmethyl group), or an aryl group.

The preferred specific examples of the groups include the ether groups or the ester groups of tertiary alkyl groups such as a t-butyl group, a t-amyl group, a 1-alkyl-1-cyclohexyl group, a 2-alkyl-2-adamantyl group, a 2-adamantyl-2-propyl group, and a 2-(4-methylcyclohexyl)-2-propyl group, acetal groups or acetal ester groups such as a 1-alkoxy-1-ethoxy group and a tetrahydropyranyl group, a t-alkylcarbonate group and a t-alkylcarbonylmethoxy group.

The specific examples of the repeating units represented by formulae (FA) to (FG) are shown below, but the invention is not restricted thereto.

The total content of the repeating units represented by formulae (FA) to (FG) is generally from 10 to 80 mol % to all the repeating units constituting the resin, preferably from 30 to 70 mol %, and more preferably from 35 to 65 mol %.

For the purpose of further improving the performances of the resist of the invention, the fluorine-based acid-decomposable resins may further be copolymerized with other polymerizable monomers in addition to the above repeating structural units.

As the usable copolymerizable monomers, compounds having one addition polymerizable unsaturated bond selected from acrylic esters, acrylamides, methacrylic esters, methacryl-amides, allyl compounds, vinyl ethers, vinyl esters, styrens, and crotonic esters other than described above are exemplified.

It is preferred that these fluorine-based acid-decomposable resins contain other repeating units as the copolymerization components besides the above repeating units having fluorine atoms from the points of improving dry etching resistance, adjusting alkali solubility, and improving adhesion with substrates. Preferred other repeating units are as follows.

1) The repeating units having an alicyclic hydrocarbon structure represented by any of formulae (pI) to (pVI) and formula (II-AB). Specifically the above exemplified repeating units 1 to 23 and repeating units [II-1] to [II-32] shown above. Preferably repeating units 1 to 23, wherein Rx represents CF₃. 2) The repeating units having a lactone structure represented by formula (Lc) and any of formulae (V-1) to (V-5). Specifically the above-exemplified repeating units, in particular, the above-exemplified repeating units represented by formula (Lc) and formulae (V-1) to (V-4). 3) The repeating units derived from the vinyl compounds having maleic anhydride, vinyl ether or a cyano group represented by the following formula (XV), (XVI) or (XVII). Specifically repeating units (C-1) to (C-15) shown below. These repeating units may or may not contain a fluorine atom.

In the above formulae, R₄₁ represents an alkyl group, a cycloalkyl group, an aralkyl group, or an aryl group, and the alkyl group represented by R₄₁ may be substituted with an aryl group.

R₄₂ represents a hydrogen atom, a halogen atom, a cyano group, or an alkyl group.

A₅ represents a single bond, a divalent alkylene group, alkenylene group, cycloalkylene group, or arylene group, or —O—CO—R₂₂—, —CO—O—R₂₃—, or —CO—N(R₂₄)—R₂₅—.

R₂₂, R₂₃ and R₂₅, which may be the same or different, each independently represents a single bond, or a divalent alkylene group, alkenylene group, cycloalkylene group or arylene group which may have an ether group, an ester group, an amido group, a urethane group or a ureido group.

R₂₄ represents a hydrogen atom, an alkyl group, a cycloalkyl group, an aralkyl group, or an aryl group.

Here, as the examples of the substituents, the same groups as the substituents in formulae (FA) to (FG) can be exemplified.

The specific examples of the repeating structural units represented by formulae (XV) to (XVII) are shown below, but the invention is not restricted thereto.

The total amount of the repeating units represented by any of formulae (XV) to (XVII) and other repeating units is generally from 0 to 70 mol % to the total repeating units constituting the resin, preferably from 10 to 60 mol %, and more preferably from 20 to 50 mol %.

The fluorine-based acid-decomposable resins may contain an acid-decomposable group in any repeating unit.

The content of a repeating unit having an acid decomposable group is preferably from 10 to 70 mol % to the total repeating units, more preferably from 20 to 60 mol %, and still more preferably from 30 to 60 mol %.

The fluorine-based acid-decomposable resins can be synthesized by radical polymerization almost similar to the synthesis of alicyclic hydrocarbon-based acid-decomposable resins.

The weight average molecular weight of the resin of component (C) is preferably from 2,000 to 200,000 as the polystyrene equivalent by the GPC method. By making the weight average molecular weight 2,000 or more, heat resistance and dry etching resistance can be improved, and by making the weight average molecular weight 200,000 or less, developability can be improved, and film-forming property can be heightened, since the viscosity becomes low. The weight average molecular weight is more preferably from 5,000 to 50,000, and still more preferably from 7,000 to 30,000. By the adjustment of the molecular weight, it is possible to reconcile the heat resistance of the composition, resolution, development failure and the like. The degree of dispersion of molecular weight (Mw/Mn) of the resin of component (C) is preferably from 1.0 to 3.0, more preferably from 1.2 to 2.5, and still more preferably from 1.2 to 1.6. By the adjustment of the degree of dispersion to a proper range, the performance of line edge roughness can be increased.

In the positive photosensitive composition in the invention, the proportion of the resin of component (C) of the invention in the entire composition is preferably from 40 to 99.99 mass % in the total solids content, more preferably from 50 to 99 mass %, and still more preferably from 80 to 96 mass %.

[4] (D) A dissolution inhibiting compound capable of decomposing by the action of an acid to increase solubility in an alkali developing solution, and having a molecular weight of 3,000 or less (hereinafter also referred to as “component (D)” or “dissolution inhibiting compound”):

As (D) the dissolution inhibiting compound capable of decomposing by the action of an acid to thereby increase the solubility in an alkali developing solution, and having a molecular weight of 3,000 or less, alicyclic or aliphatic compounds containing an acid-decomposable group, such as cholic acid derivatives containing an acid-decomposable group described in Proceeding of SPIE, 2724, 355 (1996) are preferred so as not to reduce the permeability to lights of 220 nm or less. As acid-decomposable groups and alicyclic structures, the same as those described above in the alicyclic hydrocarbon-based acid-decomposable resin are exemplified.

When the photosensitive composition of the invention is exposed with a KrF excimer laser or irradiated with electron beams, a phenolic compound having a structure that the phenolic hydroxyl group is substituted with an acid-decomposable group is preferably used. As the phenolic compounds, compounds having from 1 to 9 phenolic skeletons are preferred, and those having from 2 to 6 are more preferred.

The molecular weight of the dissolution-inhibiting compound in the invention is 3,000 or less, preferably from 300 to 3,000, and more preferably from 500 to 2,500.

The addition amount of the dissolution-inhibiting compound is preferably from 3 to 50 mass % based on the solids content of the photosensitive composition, and more preferably from 5 to 40 mass %.

The specific examples of the dissolution-inhibiting compounds are shown below, but the invention is not restricted thereto.

[5] (E) A resin soluble in an alkali developing solution (hereinafter also referred to as “component (E)” or “alkali-soluble resin”):

The alkali dissolution rate of alkali-soluble resins is preferably 20 Å/sec or more when measured with 0.261 N tetramethylammonium hydroxide (TMAH) at 23° C., and especially preferably 200 Å/sec or more.

As alkali-soluble resins for use in the invention, e.g., novolak resins, hydrogenated novolak resins, acetone-pyrogallol resins, o-polyhydroxystyrene, m-polyhydroxy-styrene, p-polyhydroxystyrene, hydrogenated polyhydroxy-styrene, halogen- or alkyl-substituted polyhydroxystyrene, hydroxystyrene-N-substituted maleimide copolymers, o/p- and m/p-hydroxystyrene copolymers, partially O-alkylated products of the hydroxyl group of polyhydroxystyrene (e.g., from 5 to 30 mol % O-methylated, O-(1-methoxy)ethylated, O-(1-ethoxy)ethylated, O-2-tetrahydropyranylated, and O-(t-butoxycarbonyl)methylated products), or partially O-acylated products (e.g., from 5 to 30 mol % o-acetylated and O-(t-butoxy)carbonylated products), styrene-maleic anhydride copolymers, styrene-hydroxystyrene copolymers, α-methylstyrene-hydroxystyrene copolymers, carboxyl group-containing methacrylic resins and derivatives thereof, and polyvinyl alcohol derivatives can be exemplified, but the invention is not limited to these resins.

Particularly preferred alkali-soluble resins are novolak resins, o-polyhydroxystyrene, m-polyhydroxystyrene p-polyhydroxystyrene, copolymers of them, alkyl-substituted polyhydroxystyrene, partially O-alkylated or O-acylated products of polyhydroxystyrene, styrene-hydroxystyrene copolymers, and α-methylstyrene-hydroxystyrene copolymers.

The novolak resins can be obtained by addition condensation to aldehydes with the prescribed monomers as main components in the presence of acid catalysts.

The weight average molecular weight of alkali-soluble resins is 2,000 or more, preferably from 5,000 to 200,000, and more preferably from 5,000 to 100,000.

Here, the weight average molecular weight is defined as the polystyrene equivalent by gel permeation chromatography.

Alkali-soluble resins (E) in the invention may be used in combination of two kinds or more.

The use amount of alkali-soluble resins is from 40 to 97 mass % based on the total solids content of the photosensitive composition, and preferably from 60 to 90 mass %.

[6] (F) An acid crosslinking agent capable of crosslinking with the alkali-soluble resin by the action of an acid (hereinafter also referred to as “component (F)” or “a crosslinking agent”):

A crosslinking agent is used in the negative photosensitive composition of the invention.

Every compound capable of crosslinking the resins soluble in an alkali developing solution by the action of an acid can be used as crosslinking agents, but the following (1) to (3) are preferably used.

(1) Hydroxymethyl body, alkoxymethyl body and acyloxymethyl body of phenol derivatives (2) Compounds having an N-hydroxymethyl group, an N-alkoxy-methyl group or an N-acyloxymethyl group (3) Compounds having an epoxy group

As the alkoxymethyl groups, those having 6 or less carbon atoms, and as the acyloxymethyl groups, those having 6 or less carbon atoms are preferred.

Of these crosslinking agents, particularly preferred compounds are shown below.

In the above formulae, L₁ to L₈, which may be the same or different, each independently represents a hydrogen atom, a hydroxymethyl group, a methoxymethyl group, an ethoxymethyl group, or an alkyl group having from 1 to 6 carbon atoms.

Crosslinking agents are used generally in proportion of from 3 to 70 mass % in the solids content of the photosensitive composition, and preferably from 5 to 50 mass %.

Other Components:

[7] (G) A basic compound:

For decreasing the fluctuation of performances during the period of time from exposure to heating, it is preferred for the photosensitive composition of the invention to contain (G) a basic compound.

As the preferred structures of basic compounds, the structures represented by any of the following formulae (A) to (E) can be exemplified.

In formula (A), R₂₅₀, R₂₅₁and R₂₅₂ each independently represents a hydrogen atom, an alkyl group having from 1 to 20 carbon atoms, a cycloalkyl group having from 3 to 20 carbon atoms, or an aryl group having from 6 to 20 carbon atoms, and R₂₅₀ and R₂₅₁ may be bonded to each other to form a ring. These groups may have a substituent, and as the alkyl group and cycloalkyl group having a substituent, an aminoalkyl group having from 1 to 20 carbon atoms or an aminocycloalkyl group having from 3 to 20 carbon atoms, a hydroxyalkyl group having from 1 to 20 carbon atoms or a hydroxycycloalkyl group having from 3 to 20 carbon atoms are preferred.

These groups may contain an oxygen atom, a sulfur atom or a nitrogen atom in the alkyl chain.

In formula (E), R₂₅₃, R₂₅₄, R₂₅₅ and R₂₅₆ each independently represents an alkyl group having from 1 to 6 carbon atoms, or a cycloalkyl group having from 3 to 6 carbon atoms.

As the preferred examples of basic compounds, guanidine, aminopyrrolidine, pyrazole, pyrazoline, piperazine, aminomorpholine, aminoalkylmorpholine, and piperidine can be exemplified, and these compounds may have a substituent. As further preferred compounds, compounds having an imidazole structure, a diazabicyclo structure, an onium hydroxide structure, an onium carboxylate structure, a trialkylamine structure, an aniline structure, or a pyridine structure, alkylamine derivatives having a hydroxyl group and/or an ether bond, and aniline derivatives having a hydroxyl group and/or an ether bond can be exemplified.

As the compounds having an imidazole structure, imidazole, 2,4,5-triphenylimidazole, and benzimidazole can be exemplified. As the compounds having a diazabicyclo structure, 1,4-diazabicyclo[2.2.2]octane, 1,5-diazabicyclo[4.3.0]non-5-ane, and 1,8-diazabicyclo[5.4.0]undeca-7-ene can be exemplified. As the compounds having an onium hydroxide structure, triarylsulfonium hydroxide, phenacylsulfonium hydroxide, sulfonium hydroxide having a 2-oxoalkyl group, specifically triphenylsulfonium hydroxide, tris(t-butyl-phenyl)sulfonium hydroxide, bis(t-butylphenyl)iodonium hydroxide, phenacylthiophenium hydroxide, and 2-oxopropyl-thiophenium hydroxide can be exemplified. The compounds having an onium carboxylate structure are compounds having an onium hydroxide structure in which the anionic part is carboxylated, e.g., acetate, adamantane-1-carboxylate, and perfluoroalkyl carboxylate are exemplified. As the compounds having a trialkylamine structure, tri(n-butyl)amine and tri(n-octyl)amine can be exemplified. As the aniline compounds, 2,6-diisopropylaniline and N,N-dimethylaniline can be exemplified. As the alkylamine derivatives having a hydroxyl group and/or an ether bond, ethanolamine, diethanol-amine, triethanolamine, and tris(methoxyethoxyethyl)amine can be exemplified. As the aniline derivatives having a hydroxyl group and/or an ether bond, N,N-bis(hydroxyethyl)-aniline can be exemplified.

These basic compounds are used alone or in combination of two or more. However, when the use amount of component (B) is 0.05 mass % or more, a basic compound may not be used. When a basic compound is used, the use amount of the basic compound is generally from 0.001 to 10 mass % based on the solids content of the photosensitive composition, and preferably from 0.01 to 5 mass %. For obtaining a sufficient addition effect, the addition amount is preferably 0.001 mass % or more, and in view of sensitivity and the developability of a non-exposed area, the addition amount is preferably 10 mass % or less.

[8] (H) Surfactant:

It is preferred for the photosensitive composition in the invention to further contain a surfactant, and it is more preferred to contain either one, or two or more, of fluorine and/or silicon surfactants (a fluorine surfactant, a silicon surfactant, a surfactant containing both a fluorine atom and a silicon atom).

By containing a surfactant, it becomes possible for the photosensitive composition in the invention to provide a resist pattern excellent in sensitivity and resolution, and low in defects in adhesion and development in using an exposure light source of 250 nm or lower, in particular, 220 nm or lower.

These fluorine and/or silicon surfactants are disclosed, e.g., in JP-A-62-36663, JP-A-61-226746, JP-A-61-226745, JP-A-62-170950, JP-A-63-34540, JP-A-7-230165, JP-A-8-62834, JP-A-9-54432, JP-A-9-5988, JP-A-2002-277862, U.S. Pat. Nos. 5,405,720, 5,360,692, 5,529,881, 5,296,330, 5,436,098, 5,576,143, 5,294,511 and 5,824,451. The commercially available surfactants shown below can also be used as they are.

As the commercially available fluorine or silicon surfactants usable in the invention, e.g., Eftop EF301 and EF303 (manufactured by Shin-Akita Kasei Co., Ltd.), Fluorad FC 430, 431 and 4430 (manufactured by Sumitomo 3M Limited), Megafac F171, F173, F176, F189, F113, F110, F177, F120, and R08 (manufactured by Dainippon Ink and Chemicals Inc.), Sarfron S-382, SC 101, 102, 103, 104, 105 and 106 (manufactured by ASAHI GLASS CO., LTD.), Troy Sol S-366 (manufactured by Troy Chemical Co., Ltd.), GF-300 and GF-150 (manufactured by TOAGOSEI CO., LTD.), Sarfron S-393 (manufactured by SEIMI CHEMICAL CO., LTD.), Eftop EF121, EF122A, EF122B, RF122C, EF125M, EF135M, EF351, 352, EF801, EF802, and EF601 (manufactured by JEMCO INC.), PF636, PF656, PF6320 and PF6520 (manufactured by OMNOVA), and FTX-204D, 208G, 218G, 230G, 204D, 208D, 212D, 218, and 222D (manufactured by NEOS) are exemplified. In addition, polysiloxane polymer KP-341 (manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used as a silicon surfactant.

In addition to these known surfactants as exemplified above, surfactants using polymers having fluoro-aliphatic groups derived from fluoro-aliphatic compounds manufactured by a telomerization method (also called a telomer method) or an oligomerization method (also called an oligomer method) can be used. The fluoro-aliphatic compounds can be synthesized by the method disclosed in JP-A-2002-90991.

As the polymers having fluoro-aliphatic groups, copolymers of monomers having fluoro-aliphatic groups and (poly(oxyalkylene)) acrylate and/or (poly(oxyalkylene)) methacrylate are preferred, and they may be distributed at random or block copolymerized. As the poly(oxyalkylene) groups, a poly(oxyethylene) group, a poly(oxypropylene) group, and a poly(oxybutylene) group are exemplified. Further, the polymers may be units having alkylenes different in chain length in the same chain length, such as a block combination of poly(oxyethylene and oxypropylene and oxyethylene), and a block combination of poly(oxyethylene and oxypropylene). In addition, copolymers of monomers having fluoro-aliphatic groups and poly(oxyalkylene) acrylate (or methacrylate) may be not only bipolymers but also terpolymers or higher polymers obtained by copolymerization of monomers having different two or more kinds of fluoro-aliphatic groups or different two or more kinds of poly(oxyalkylene) acrylates (or methacrylates) at the same time.

For example, as commercially available surfactants, Megafac F178, F470, F473, F475, F476 and F472 (manufactured by Dainippon Ink and Chemicals Inc.) can be exemplified. Further, copolymers of acrylate (or methacrylate) having a C₆F₁₃ group and poly(oxyalkylene) acrylate (or methacrylate), and copolymers of acrylate (or methacrylate) having a C₃F₇ group, poly(oxyethylene) acrylate (or methacrylate), and poly(oxypropylene) acrylate (or methacrylate) are exemplified.

In the invention, surfactants other than fluorine and/or silicon surfactants can also be used. Specifically, nonionic surfactants, such as polyoxyethylene alkyl ethers, e.g., polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, etc., polyoxyethylene alkylallyl ether, e.g., polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether, etc., polyoxyethylene-polyoxypropylene block copolymers, sorbitan fatty acid esters, e.g., sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, sorbitan tristearate, etc., and polyoxyethylene sorbitan fatty acid esters, e.g., polyoxy-ethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan tristearate, etc., can be exemplified.

These surfactants may be used alone or may be used in combination of some kinds.

The use amount of surfactants is preferably in proportion of from 0.01 to 10 mass % to the total amount of the positive resist composition (excluding solvents), and more preferably from 0.1 to 5 mass %.

[9] (I) Organic solvent:

The above components of the photosensitive composition of the invention are dissolved in a prescribed organic solvent.

As the organic solvents usable in the invention, ethylene dichloride, cyclohexanone, cyclopentanone, 2-heptanone, γ-butyrolactone, methyl ethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, toluene, ethyl acetate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethyl ethoxypropionate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and tetrahydrofuran are exemplified.

(Ia) Ketone Solvents:

Solvents containing at least a ketone structure are preferably used in the invention.

As the solvents containing a ketone structure, chain-like ketone solvents and cyclic ketone solvents are exemplified, and those having from 5 to 8 carbon atoms are preferred for capable of obtaining good coating property.

As the chain-like ketone solvents, e.g., 2-heptanone, methyl ethyl ketone, methyl isobutyl ketone, etc., are exemplified, and 2-heptanone is preferred.

As the cyclic ketone solvents, e.g., cyclopentanone, 3-methyl-2-cyclopentanone, cyclohexanone, 2-methylcyclo-hexanone, 2,6-dimethylcyclohexanone, cycloheptanone, cyclooctanone, isophorone, etc., are exemplified, and cyclohexanone and cycloheptanone are preferred.

It is preferred that the solvents having a ketone structure are used alone, or as mixed solvents with other solvents. As the solvents to be mixed (combined use solvents), propylene glycol monoalkyl ether carboxylate, alkyl lactate, propylene glycol monoalkyl ether, alkyl alkoxypropionate, lactone compounds, etc., can be exemplified.

As the propylene glycol monoalkyl ether carboxylate, e.g., propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether propionate, propylene glycol monoethyl ether acetate, etc., can be exemplified.

As the alkyl lactate, e.g., methyl lactate, ethyl lactate, etc., can be exemplified.

As the propylene glycol monoalkyl ether, e.g., propylene glycol monomethyl ether and propylene glycol monoethyl ether, etc., can be exemplified.

As the alkyl alkoxypropionate, e.g., methyl methoxy-propionate, ethyl methoxypropionate, methyl ethoxypropionate, ethyl ethoxypropionate, etc., can be exemplified.

As the lactone compounds, e.g., γ-butyrolactone, etc., can be exemplified.

As preferred combined use solvent, propylene glycol monoalkyl ether carboxylate, alkyl lactate and propylene glycol monoalkyl ether can be exemplified, and as more preferred combined use solvent, propylene glycol monomethyl ether acetate can be exemplified.

By the use of mixed solvents of ketone solvents and combined use solvents, substrate adhesion, developability and DOF are improved.

The ratio of the ketone solvent and the combined use solvent (mass ratio) is preferably from 10/90 to 95/5, more preferably from 20/80 to 80/20, and still more preferably from 30/70 to 70/30.

In view of heightening uniform film thickness and resistance to development failure, high boiling point solvents having a boiling point of 200° C. or higher, e.g., ethylene carbonate, propylene carbonate, etc., may be mixed.

The addition amount of these high boiling point solvents is generally from 0.1 to 15 mass % in all the solvents, preferably from 0.5 to 10 mass %, and more preferably from 1 to 5 mass %.

In the invention, a photosensitive composition having solids content concentration of generally from 3 to 25 mass %, preferably from 5 to 22 mass %, and more preferably from 5 to 15 mass % is prepared with a single solvent, preferably two or more solvents.

Other Additives:

If necessary, dyes, plasticizers, surfactants other than the surfactants of component (H), photosensitizers, and compounds for expediting the dissolution of composition in a developing solution may be further added to the photosensitive composition in the present invention.

Compounds for expediting dissolution in a developing solution that can be used in the invention are low molecular weight compounds having a molecular weight of 1,000 or less and having two or more phenolic OH groups or one or more carboxyl groups. When carboxyl groups are contained, alicyclic or aliphatic compounds are preferred.

The preferred addition amount of these dissolution accelerating compounds is preferably from 2 to 50 mass % based on the resin of component (C) or the resin of component (E), and more preferably from 5 to 30 mass %. The amount is preferably 50 mass % or less in the point of restraint of development residue and prevention of pattern deformation in development.

These phenolic compounds having a molecular weight of 1,000 or less can be easily synthesized with referring to the methods disclosed, e.g., in JP-A-4-122938, JP-A-2-28531, U.S. Pat. No. 4,916,210, and EP 219294.

As the specific examples of the alicyclic or aliphatic compounds having a carboxyl group, carboxylic acid derivatives having a steroid structure, e.g., cholic acid, deoxycholic acid, and lithocholic acid, adamantanecarboxylic acid derivatives, adamantanedicarboxylic acid, cyclohexanecarboxylic acid, and cyclohexanedicarboxylic acid are exemplified, but the invention is not restricted to these compounds.

Pattern Forming Method:

The photosensitive composition in the invention is used by dissolving each of the above components in a prescribed organic solvent, preferably dissolving in a mixed solvent as described above, and coating the solution on a prescribed support as follows.

For example, the photosensitive composition is coated on a substrate such as the one used in the manufacture of precision integrated circuit element (e.g., silicon/silicon dioxide coating) by an appropriate coating method with a spinner or a coater, and dried, to thereby form a photosensitive film.

The photosensitive film is irradiated with actinic ray or radiation through a prescribed mask, preferably subjected to baking (heating), and then development. Thus, a good pattern can be obtained.

At the time of irradiation with actinic ray or radiation, exposure (immersion exposure) may be performed by filling a liquid (an immersion medium) having higher refractive index than that of air between a photosensitive film and a lens, by which resolution can be raised.

As actinic rays or radiation, infrared rays, visible rays, ultraviolet rays, far ultraviolet rays, X-rays and electron beams can be exemplified, and preferably far ultraviolet rays of wavelengths of 250 nm or less, and more preferably 220 nm or less. Specifically, a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), an F₂ excimer laser (157 nm), X-rays and electron beams are exemplified, and ArF excimer lasers, F₂ excimer lasers, EUV (13 nm), and electron beams are preferred.

Immersion Exposure:

When the photosensitive composition in the invention is subjected to immersion exposure, it is preferred that the photosensitive composition is used in a thickness of from 30 to 250 nm in view of the improvement of resolution, and more preferably a thickness of from 30 to 100 nm. Such a desired thickness can be realized by setting the concentration of solids content in the photosensitive composition in a proper range and giving appropriate viscosity to thereby improve the coating property and film forming property.

The concentration of all the solids content in the photosensitive composition is generally from 1 to 10 mass %, more preferably from 1 to 8 mass %, and still more preferably from 1.0 to 6.0 mass %.

When the photosensitive composition in the invention is subjected to immersion exposure, the photosensitive composition is used by dissolving each of the above components in a prescribed organic solvent, preferably in a mixed solvent as described above, and coating the solution on a prescribed support as follows.

That is, the photosensitive composition is coated on a substrate such as the one used in the production of precision integrated circuit elements (e.g., silicon/silicon dioxide coating) by an appropriate coating method with a spinner or a coater in an arbitrary thickness (generally from 30 to 500 nm). After coating, if necessary, a resist film is washed with the immersion liquid. The washing time is generally from 5 seconds to 5 minutes.

Subsequently, the coated resist is dried by spin or bake to form a resist film, and the resist film formed is subjected to exposure (immersion exposure) for pattern formation through a mask via an immersion liquid. For example, exposure is performed in the state of filling an immersion liquid between a resist film and an optical lens. The exposure dose can be optionally set, but is generally from 1 to 100 mJ/cm². After exposure, if necessary, the resist film is washed with the immersion liquid. The washing time is generally from 5 seconds to 5 minutes. After that, the resist film is preferably subjected to spin or/and bake, development and rinsing, whereby a good pattern can be obtained. It is preferred to perform bake, and the temperature of bake is generally from 30 to 300° C. The time from exposure to bake process is preferably shorter from the viewpoint of PED.

The exposure rays here are far ultraviolet rays of wavelengths of preferably 250 nm or less, and more preferably 220 nm or less. Specifically, a KrF excimer laser (248 nm), an ArF excimer laser (193 nm), an F₂ excimer laser (157 nm), and X-rays are exemplified.

Incidentally, the variation of performances of a resist at the time when subjected to immersion exposure is thought to be resulting from the contact of a resist surface with an immersion liquid.

An immersion liquid for use in immersion exposure is described below.

An immersion liquid for use in immersion exposure preferably has a temperature coefficient of refractive index as small as possible so as to be transparent to the exposure wavelength and to hold the distortion of an optical image reflected on the resist at the minimum. In particular, when the exposure light source is an ArF excimer laser (wavelength: 193 nm), it is preferred to use water as the immersion liquid for easiness of availability and capable of handling easily, in addition to the above points.

It is also possible to use a medium having a refractive index of 1.5 or more for capable of improving the refractive index. The medium may be an aqueous solution or an organic solvent.

When water is used as the immersion liquid, to reduce the surface tension of water and to increase the surface activity, a trace amount of additive (a liquid) that does not dissolve the resist layer on a wafer and has a negligible influence on the optical coating of the underside of a lens element may be added. As such additives, aliphatic alcohols having a refractive index almost equal to the refractive index of water are preferred, specifically methyl alcohol, ethyl alcohol and isopropyl alcohol are exemplified. By adding an alcohol having a refractive index almost equal to that of water, even if the alcohol component in water is evaporated and the concentration of the content is changed, the refractive index variation of the liquid as a whole can be made extremely small. On the other hand, when impurities opaque to the light of 193 nm or substances largely different from water in a refractive index are mixed, these substances bring about the distortion of an optical image reflected on the resist. Accordingly the water to be used is preferably distilled water. Further, pure water filtered through an ion exchange filter may be used.

The electric resistance of water is preferably 18.3 MΩ·cm or higher, and TOC (total organic material concentration) is preferably 20 ppb or lower, and it is preferred that water has been subjected to deaeration treatment.

It is possible to heighten lithographic performance by increasing the refractive index of an immersion liquid. From such a point of view, additives capable of increasing the refractive index may be added to water, or heavy water (D₂O) may be used in place of water.

A film hardly soluble in an immersion liquid (hereinafter also referred to as “topcoat”) may be provided between a resist film by the positive resist composition of the invention and an immersion liquid so as not to bring the resist film into direct contact with the immersion liquid. The necessary functions required of the topcoat are the aptitude for coating on the upper layer of a resist, the transparency to radiation, in particular the transparency to the ray of 193 nm, and the insolubility in an immersion liquid. It is preferred that the topcoat is not mixed with a resist and can be coated uniformly on a resist upper layer.

From the viewpoint of the transparency to 193 nm, a polymer not containing an aromatic group is preferred as the topcoat. Specifically, hydrocarbon polymers, acrylic ester polymers, polymethacrylic acid, polyacrylic acid, polyvinyl ether, silicon-containing polymers, and fluorine-containing polymers are exemplified. Considering that impurities eluting from a topcoat to the immersion liquid contaminate the optical lens, the residual monomer components of the polymer contained in the topcoat is preferably less.

When the topcoat is peeled off, a developing solution may be used, or a remover may be used separately. As the remover, a solvent low in penetration into a resist is preferred. In view of capable of performing a peeling process at the same time with the development process of a resist, it is preferred that the topcoat can be peeled off by an alkali developing solution. From the viewpoint of performing peeling with an alkali developing solution, the topcoat is preferably acidic, but from the viewpoint of non-intermixture with the resist, it may be neutral or alkaline.

Resolution increases when there is no difference in the refractive indexes between the topcoat and the immersion liquid. When water is used as the immersion liquid in ArF excimer laser (wavelength: 193 nm) exposure, it is preferred that the refractive index of the topcoat for ArF immersion exposure is nearer the refractive index of the immersion liquid. For bringing the refractive index of the topcoat nearer to that of the immersion liquid, it is preferred for the topcoat to contain a fluorine atom. Further, from the viewpoint of the transparency and refractive index, the thickness of the topcoat is preferably thinner.

It is preferred that a topcoat should not be mixed with a resist, and further not mixed with an immersion liquid. From this point of view, when water is used as the immersion liquid, the solvent for a topcoat is preferably hardly soluble in the solvent of the resist and a nonaqueous medium. Further, when an immersion liquid is an organic solvent, the topcoat may be aqueous or nonaqueous.

A resist composition in the invention as formed to a resist film has the receding contact angle of water to the resist film of preferably 65° or more. Here, the receding contact angle is the angle under normal temperature and atmospheric pressure. The receding contact angle is the contact angle of going back at the time when a resist film is inclined and a droplet begins to drop.

In a development process, a developing solution is used as follows. As the alkali developing solution of a resist composition, alkaline aqueous solutions of inorganic alkalis, e.g., sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, aqueous ammonia, etc., primary amines, e.g., ethylamine, n-propylamine, etc., secondary amines, e.g., diethylamine, di-n-butylamine, etc., tertiary amines, e.g., triethylamine, methyldiethylamine, etc., alcohol amines, e.g., dimethylethanolamine, triethanolamine, etc., quaternary ammonium salts, e.g., tetramethylammonium hydroxide, tetraethylammonium hydroxide, etc., and cyclic amines, e.g., pyrrole, piperidine, etc., can be used.

An appropriate amount of alcohols and surfactants may be added to these alkali developing solutions.

The alkali concentration of an alkali developing solution is generally from 0.1 to 20 mass %.

The pH of an alkali developing solution is generally from 10.0 to 15.0.

EXAMPLE

The invention will be described in further detail with reference to examples, but the invention is not restricted thereto.

Synthesis of Compound (A-1):

A mixture comprising 1.93 g (15.8 mmol) of 4-hydroxybenzaldehyde, 5.0 g (15.8 mol) of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, 1.76 g of triethylamine, and 70 ml of THF was stirred under nitrogen current at room temperature for 7 hours. To the mixture were added 200 ml of water and 200 ml of ethyl acetate, the organic layer was washed with water, a saturated sodium chloride aqueous solution, and water in the order, and the organic layer was dried with sodium sulfate. The solvent was concentrated to obtain an oily compound. The oily compound was dissolved in 50 ml of methanol and 50 ml of a 1M sodium hydroxide aqueous solution, and the solution was stirred at room temperature for 3 hours. To the solution were added 200 ml of water and 200 ml of ethyl acetate, the organic layer was washed with water, a saturated sodium chloride aqueous solution, and water in the order, and the organic layer was dried with sodium sulfate. The solvent was concentrated, the residue was dissolved in 150 ml of methanol, and 2.68 g of triphenylsulfonium bromide was added to the solution, and followed by stirring at room temperature for 3 hours. Chloroform (200 ml) was added to the solution, the organic layer was washed with water, and the residue was purified by column chromatography (SiO₂, chloroform/methanol: 10/1) to thereby obtain 4.68 g of an objective oily compound.

¹H-NMR (400 MHz, CDCl₃) δ 7.55 (d, 2H), 7.27-7.76 (m, 15H), 7.95 (d, 2H), 10.03 (s, 1H)

¹⁹F-NMR (400 MHz, CDCl₃) δ −118 (t, 2F), −114 (m, 2F), −107 (m, 2F)

Synthesis of Compound (A-2):

A mixture comprising 5.26 g (31.6 mmol) of ethyl 4-hydroxybenzoate, 10.0 g (31.6 mol) of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, 50 ml of triethylamine, and 40 ml of THF was stirred under nitrogen current at room temperature for 20 hours. After adding 100 ml of water and 200 ml of ethyl acetate to the mixture and stirring the mixture for 1 hour, the organic layer was washed with water, a saturated sodium chloride aqueous solution, and water in the order, and the organic layer was concentrated. The residue was dissolved in 200 ml of methanol, and 9.76 g of triphenylsulfonium bromide was added thereto, followed by stirring at room temperature for 3 hours. Chloroform (200 ml) was added to the solution, the organic layer was washed with water to be concentrated. The resulting product was dissolved in 50 ml of methanol and 30 ml of a 1M sodium hydroxide aqueous solution, and followed by stirring at room temperature for 2 hours. After neutralizing the resulting product with a 1M hydrochloric acid aqueous solution, 200 ml of chloroform was added thereto, the organic layer was washed with water to be concentrated. The residue was washed with ethyl acetate to thereby obtain 1.50 g of an objective oily compound.

¹H-NMR (400 MHz, CDCl₃) δ 7.44 (d, 2H), 7.79-7.90 (m, 15H), 8.315 (d, 2H)

¹⁹F-NMR (400 MHz, CDCl₃) δ −119 (t, 2F), −115 (m, 2F), −109 (m, 2F)

Synthesis of Compound (A-6):

A mixture comprising 3.26 g (15.8 mmol) of 4-hydroxy-3,5-diisopropylbenzaldehyde (synthesized according to the method described in J. Med. Chem., 31 (1), 122-129 (1988)), 5.0 g (15.8 mol) of 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl difluoride, 30 ml of triethylamine, and 10 ml of THF was stirred under nitrogen current at 50° C. for 9 hours. To the mixture were added 200 ml of water and 200 ml of ethyl acetate, the organic layer was washed with water, a saturated sodium chloride aqueous solution, and water in the order, and the organic layer was dried with sodium sulfate. The solvent was concentrated to thereby obtain an oily compound. The oily compound was dissolved in 50 ml of methanol and 50 ml of a 1M sodium hydroxide aqueous solution, and the solution was stirred at room temperature for 2 hours. To the solution were added 200 ml of water and 200 ml of ethyl acetate, the organic layer was washed with water, a saturated sodium chloride aqueous solution, and water in the order, and the organic layer was dried with sodium sulfate. The solvent was concentrated, the residue was dissolved in 50 ml of methanol, and 4.61 g of triphenylsulfonium bromide was added thereto, followed by stirring at room temperature for 3 hours. Chloroform (200 ml) was added to the solution, the organic layer was washed with water, and the residue was purified by column chromatography (SiO₂, chloroform/methanol: 10/1) to thereby obtain 6.33 g of an objective oily compound.

¹H-NMR (400 MHz, CDCl₃) δ 1.25 (d, 12H), 4.39 (quintet, 2H), 7.27-7.77 (m, 17H), 10.00 (s, 1H)

¹⁹F-NMR (400 MHz, CDCl₃) δ −118 (t, 2F), −114 (m, 2F), −107 (m, 2F)

Other compounds (A) were also synthesized in the same manner.

Resin C:

The structure, molecular weight and degree of molecular weight dispersion of each resin (C) used in Examples are shown below. The number on the right hand of the repeating unit is a molar ratio, and the rest is the same as above.

Examples ArF1 to ArF15 and Comparative Examples ArF1r to ArF5r Preparation of Resist:

Each solution having the concentration of solids content of 12 mass % was prepared by dissolving the components in the solvents respectively shown in Table 2 below, and a positive resist solution was prepared by filtrating the above-prepared solution through a polytetrafluoroethylene filter or a polyethylene filter having a pore size of 0.1 μm. The thus prepared positive resist solution was evaluated as follows. The results obtained are shown in Table 2.

Evaluation of Resist: Exposure Condition (1)

An antireflection film DUV-42 (manufactured by Brewer Science) was uniformly coated on a silicon substrate having been subjected to hexamethyldisilazane treatment in a thickness of 600 Å by a spin coater, and was dried on a hot plate at 100° C. for 90 seconds, and then dried by heating at 190° C. for 240 seconds. After that, each positive resist solution was coated thereon by a spin coater and dried at 120° C. for 90 seconds to form a resist film having a thickness of 0.25 μm.

The resist film was subjected to exposure through a mask with an ArF excimer laser stepper (NA: 0.6, manufactured by ISI Co.), and heated on a hot plate at 120° C. for 90 seconds just after exposure. Further, the resist film was developed with a 2.38 mass % tetramethylammonium hydroxide aqueous solution at 23° C. for 60 seconds, rinsed with pure water for 30 seconds, and then dried, whereby a line pattern was formed.

Exposure Condition (2)

In condition (2), a resist pattern was formed by immersion exposure with pure water.

An organic antireflection film ARC29A (manufactured by Nissan Chemical Industries, Ltd.) was coated on a silicon wafer, and the coated layer was baked at 205° C. for 60 seconds to form an antireflection film having a thickness of 78 nm. Each positive resist solution prepared was coated on the antireflection film and baked at 120° C. for 60 seconds, whereby a resist film having a thickness of 250 nm was formed. The obtained wafer was subjected to pattern exposure with an ArF excimer laser immersion scanner (NA: 0.75). Super pure water of impurities of 5 ppb or less was used as the immersion liquid. After that, the resist film was heated at 120° C. for 60 seconds, developed with a 2.38 mass % tetramethylammonium hydroxide aqueous solution for 30 seconds, rinsed with pure water, and then dried by spinning to obtain a resist pattern.

Resist patterns were formed by exposure conditions (1) and (2) and evaluated as follows.

Pattern Profile:

In exposure conditions (1) and (2), taking the exposure amount required to reproduce line and space of 1/1 of a mask size of 130 nm as the optimal exposure amount, a profile at the optimal exposure amount was observed with a scanning electron microscope (SEM).

Pattern Collapse:

When exposure was performed at an optimal exposure amount, the line width resolved without accompanied by pattern collapse in a finer mask size was taken as the line width of critical pattern collapse. The smaller the value, the finer pattern is resolved without collapsing, that is, pattern collapse occurs with difficulty.

TABLE 2 ArF Positive Dissolution Acid Generator Acid Generator Used Resin Basic Compound Surfactant Solvent Inhibiting Example (A) (g) in Combination (g) (10 g) (g) (0.03 g) (mass ratio) Compound (g) ArF-1 A-1 (0.1) z68 (0.4) RA-23 PEA/TPA W-4 A1/B1 (0.02/0.02) (60/40) ArF-2 A-2 (0.2) z66 (0.3) RA-1 DIA (0.03) W-4 A1/B1 (60/40) ArF-3 A-4 (0.2) z65 (0.4) RA-4 PEA (0.02) W-4 A1/B1 (70/30) ArF-4 A-6 (0.3) z63 (0.15) RA-24 PEA (0.02) W-4 A1/A4 (60/40) ArF-5 A-8 (0.2) z60 (0.3) RA-20 PEA/DIA W-4 A1/B1 (0.02/0.02) (60/40) ArF-6 A-9 (0.3) z34 (0.4) RA-1 PEA (0.02) W-4 A1/B1 LCB (0.2) (60/40) ArF-7 A-10 (0.3) z78 (0.2) RA-22 PEA/DIA W-4 A1/B1 (0.02/0.02) (80/20) ArF-8 A-15 (0.4) z60 (0.2) RA-20 PEA (0.02) W-4 A1/B2 (60/40) ArF-9 A-17 (0.5) z64, 38 (0.3/0.4) RA-24 DIA (0.02) W-1 A1/B1 (60/40) ArF-10 A-25 (0.3) z78 (0.3) RA-24 PEA (0.02) W-4 A1/B1 (80/20) ArF-11 A-32 (0.2) z38, 63 (0.4/0.4) RA-22 PEA (0.02) W-4 A1/A3 LCB (0.2) (60/40) ArF-12 A-6 (0.3) — (—) RA-25 — (—) — A1/B1 (60/40) ArF-13 A-6 (0.4) z38 (0.3) RA-4 PEA/DIA W-4 A1/B2 (0.01/0.01) (80/20) ArF-14 A-73 (0.4) z78 (0.4) RA-20 PEA 0.02 W-4 A1/B1 80/20 ArF-15 A-6/A-79 z60 (0.2) RA-1/RA-20 PEA/DIA W-4 A1/B1 (0.3/0.2) (1/1) (0.01/0.01) (60/40) Exposure Condition (I) Exposure Condition (II) Pattern Pattern Collapse Pattern Collapse Pattern Example (nm) Profile (nm) Profile ArF-1 65 Rectangle 62 Rectangle ArF-2 71 Rectangle 55 Rectangle ArF-3 65 Rectangle 53 Rectangle ArF-4 65 Rectangle 53 Rectangle ArF-5 68 Rectangle 58 Rectangle ArF-6 61 Rectangle 65 Rectangle ArF-7 64 Rectangle 63 Rectangle ArF-8 69 Rectangle 66 Rectangle ArF-9 66 Rectangle 70 Rectangle ArF-10 68 Rectangle 62 Rectangle ArF-11 57 Rectangle 55 Rectangle ArF-12 61 Rectangle 58 Rectangle ArF-13 55 Rectangle 61 Rectangle ArF-14 64 Rectangle 65 Rectangle ArF-15 63 Rectangle 69 Rectangle Dissolution Inhibiting Comparative Acid Generator Acid Generator Used Resin Basic Compound Surfactant Solvent Compound Example (A) (g) in Combination (g) (10 g) (g) (0.03 g) (mass ratio) (g) ArF-1r — (—) z38 (0.4) RA-5 PEA (0.03) W-4 A1/B1 (60/40) ArF-2r TPSB (0.4) z60 (0.4) RA-23 PEA/DIA W-4 A1/B1 (0.02/0.01) (80/20) ArF-3r TPSPB (0.3) z63 (0.4) RA-20 DIA (0.03) W-4 A1/A3 (60/40) ArF-4r TPS-1 (0.3) z34 (0.25) RA-4 PEA (0.03) W-4 A1/A3 LCB (0.2) (60/40) ArF-5r TPS-2 (0.3) z66 (0.4) RA-24 PEA (0.03) W-4 A1/A3 (60/40) ArF-6r TPS-3 (0.3) z60 (0.3) RA-1 TMEA (0.03) W-1 A1/B1 80/20) Exposure Condition (I) Exposure Condition (II) Pattern Pattern Comparative Collapse Pattern Collapse Pattern Example (nm) Profile (nm) Profile ArF-1r 95 Taper 93 Taper ArF-2r 102 Reverse taper 88 Taper ArF-3r 92 Taper 96 Reverse taper ArF-4r 96 Reverse taper 109 Taper ArF-5r 98 Taper 87 Taper ArF-6r 99 Taper 96 Reverse taper

The abbreviations common to each table are enumerated together below.

Comparative Compounds:

The abbreviations of comparative compounds used in Comparative Examples are as follows.

-   TPSB: Triphenylsulfonium pentafluorobenzenesulfonate

-   TPSPB: Triphenylsulfonium perfluorobutanesulfonate

Basic Compounds:

-   TPI: 2,4,5-Triphenylimidazole -   TPSA: Triphenylsulfonium acetate -   HEP: N-Hydroxyethylpiperidine -   DIA: 2,6-Diisopropylaniline -   DCMA: Dicyclohexylmethylamine -   TPA: Tripentylamine -   HAP: Hydroxyantipyrine -   TBAH: Tetrabutylammonium hydroxide -   TMEA: Tris(methoxyethoxyethyl)amine -   PEA: N-Phenyldiethanolamine -   TOA: Trioctylamine -   DBN: 1,5-Diazabicyclo[4.3.0]nona-5-ene

Surfactants:

-   W-1: Megafac F176 (fluorine surfactant, manufactured by Dainippon     Ink and Chemicals Inc.) -   W-2: Megafac R08 (fluorine/silicon surfactant, manufactured by     Dainippon Ink and Chemicals Inc.) -   W-3: Polysiloxane polymer KP-341 (silicon surfactant, manufactured     by Shin-Etsu Chemical Co., Ltd.) -   W-4: Troy Sol S-366 (manufactured by Troy Chemical Co., Ltd.)

Solvents:

-   A1: Propylene glycol monomethyl ether acetate -   A2: 2-Heptanone -   A3: Cyclohexanone -   A4: γ-Butyrolactone -   B1: Propylene glycol monomethyl ether -   B2: Ethyl lactate

Dissolution Inhibiting Compound:

-   LCB: t-Butyl lithocholate

From the results shown in Table 2, it is apparent that the photosensitive compositions in the invention are excellent in ArF ordinary exposure and ArF immersion exposure.

Examples Si-1 to Si-7 and Comparative Examples Si-1r to Si-6r (1) Formation of Lower Resist Layer

FHi-028DD resist (resist for i-ray, manufactured by Fuji Film Olin Co., Ltd.) was coated on a 6 inch silicon wafer with a spin coater Mark 8 (a product of Tokyo Electron Limited), baked at 90° C. for 90 seconds, whereby a uniform film having a thickness of 0.55 μm was obtained.

The obtained film was further heated at 200° C. for 3 minutes to thereby form a lower resist layer having a thickness of 0.40 μm.

(2) Formation of Upper Resist Layer

Each solution having the concentration of solids content of 11 mass % was prepared by dissolving the components in the solvents respectively shown in Table 3 below. The obtained solution was filtrated through a membrane filter having a pore diameter of 0.1 μm, whereby a composition for an upper resist layer was prepared.

The composition for an upper resist layer was coated on the lower resist layer in the same manner as in the lower layer, and heated at 130° C. for 90 seconds, whereby an upper resist layer having a thickness of 0.20 μm was formed.

Resins (SI-1) to (SI-5) in Table 3 are as follows.

Molecular Weight (SI-1)

15000 (SI-2)

14500 (SI-3)

 9600 (SI-4)

 8900 (SI-5)

10800

(3) Evaluation of Resist

The thus-obtained wafer was subjected to exposure with ArF Excimer Stepper 9300 (a product of ISI Co.) attached with a resolution mask with varying the exposure amount.

Subsequently, after heating at 120° C. for 90 seconds, the wafer was developed with a 2.38 mass % tetrahydroammonium hydroxide developing solution for 60 seconds, rinsed with distilled water and dried to form an upper layer pattern. The resist was evaluated in the same manner as in Example ArF-1.

The results obtained are shown in Table 3 below.

TABLE 3 Silicon-Containing Positive Resist Acid Acid Generator Dissolution Generator Used in Basic Inhibiting Pattern (A) Combination Resin Compound Surfactant Solvent Compound Collapse Pattern (g) (g) (10 g) (g) (0.03 g) (mass ratio) (g) (nm) Profile Ex. No. Si-1 A-1 (0.3) z38 (0.4) SI-1 PEA (0.02) W-4 A1/A3 (60/40) 58 Rectangle Si-2 A-2 (0.3) z60 (0.35) SI-4 TPA (0.03) W-1 A1/A3 (60/40) 59 Rectangle Si-3 A-4 (0.3) z78 (0.3) SI-3 TPA (0.03) W-4 A1 (100) 57 Rectangle Si-4 A-6 (0.4) z38 (0.4) SI-2 DIA (0.03) W-3 A1 100) 63 Rectangle Si-5 A-8 (0.3) z60 (0.3) SI-2 PEA/DIA W-4 A1 (100) 65 Rectangle (0.01/0.01) Si-6 A-32 (0.3) z78 (0.3) SI-2 DIA (0.02) W-4 A1/A3 (60/40) 64 Rectangle Si-7 A-73 (0.3) z38 (0.3) SI-4 PEA (0.02) W-4 A1 (100) 61 Rectangle Comparative Ex. No. Si-1r — (—) z38 (0.4) SI-1 PEA (0.02) W-4 A1 (100) 95 Taper Si-2r TPSB (0.4) z60 (0.4) SI-2 DIA (0.03) W-4 A1/B1 (80/20) 89 Reverse Taper Si-3r TPSPB z63 (0.4) SI-3 PEA (0.03) W-4 A1 (100) 99 Taper (0.3) Si-4r TPS-1 (0.3) z34 (0.25) SI-4 PEA (0.03) W-4 A1 (100) 87 Reverse Taper Si-5r TPS-2 (0.3) z66 (0.4) SI-5 DIA (0.03) W-1 A1/A3 (60/40) 97 Taper Si-6r TPS-3 (0.3) z60 (0.3) SI-3 TPA (0.04) W-4 A1/A3 (60/40) 102 Taper

From the results shown in Table 3, it is apparent that the photosensitive compositions in the invention are also excellent when used as two-layered resists.

Examples KrFp-1 to KrFp-7 and Comparative Examples KrFp-1r to KrFp-6r Preparation of Resist:

Each positive resist solution having the concentration of solids content of 14 mass % was prepared by dissolving the components in the solvents respectively shown in Table 4 below, and filtrating the solution through a polytetrafluoroethylene filter having a pore size of 0.1 μm.

Evaluation of Resist:

The prepared positive resist solution was uniformly coated on a silicon substrate having been subjected to hexamethyldisilazane treatment by a spin coater, and dried by heating on a hot plate at 120° C. for 90 seconds to form a resist film having a thickness of 0.4 μm.

The resist film was subjected to pattern exposure through a mask for line and space with a KrF excimer laser stepper (NA: 0.63), and heated on a hot plate at 110° C. for 90 seconds just after exposure. Further, the resist film was developed with a 2.38 mass % tetramethylammonium hydroxide aqueous solution at 23° C. for 60 seconds, rinsed with pure water for 30 seconds, and then dried, whereby a line pattern was formed. Each resist was evaluated in the same manner as in the evaluation by ArF exposure in Example ArF-1.

The results obtained are shown in Table 4 below.

TABLE 4 KrF Positive Acid Acid Generator Dissolution Generator Used in Solvent Inhibiting Pattern (A) Combination Resin Basic Compound (mass Compound Collapse Pattern (g) (g) (10 g) (g) Surfactant ratio) (g) (nm) Profile Ex. No. KrFp-1 A-1 (0.3) z38 (0.4) R-9 PEA (0.04) W-4 A1/B1 (60/40) 70 Rectangle KrFp-2 A-2 (0.3) z60 (0.35) R-2 PEA (0.02) W-4 A1 (100) 71 Rectangle KrFp-3 A-4 (0.3) z78 (0.3) R-7 TMEA (0.02) W-4 A1/A4 (80/20) 69 Rectangle KrFp-4 A-6 (0.4) z38 (0.4) R-8 PEA (0.04) W-4 A1/B1 (70/30) 67 Rectangle KrFp-5 A-8 (0.3) z60 (0.3) R-8 DIA (0.02) W-4 A1/B1 (60/40) 65 Rectangle KrFp-6 A-32 (0.3) z78 (0.3) R-14 PEA/DIA W-4 A1/A3 (80/20) LCB (0.1) 53 Rectangle (0.01/0.01) KrF-7 A-73 (0.5) z38 (0.3) R-14 PEA (0.02) W-1 A1/A4 (80/20) 61 Rectangle Comparative Ex. No. KrFp-1r — (—) z38 (0.4) R-9 DIA (0.03) W-4 A1/B1 (60/40) 103 Taper KrFp-2r TPSB (0.4) z60 (0.4) R-2 PEA (0.03) W-4 A1/B1 (70/30) 87 Taper KrFp-3r TPSPB z63 (0.4) R-2 DIA (0.03) W-4 A1/B1 (60/40) 90 Reverse (0.3) taper KrFp-4r TPS-1 z34 (0.25) R-7 PEA/DIA W-1 A1 (100) 99 Taper (0.3) (0.01/0.01) KrFp-5r TPS-2 z66 (0.4) R-8 PEA (0.02) W-4 A1/B1 (70/30) 86 Taper (0.3) KrFp-6r TPS-3 z60 (0.3) R-14 DIA (0.03) W-4 A1/A3 (60/40) 100 Taper (0.3)

The molar ratio of repeating units and weight average molecular weight of each of resins (R-2), (R-7), (R-8), (R-9), (R-14) and (R-17) used in Table 4 are shown in Table 5 below.

TABLE 5 Weight Molar Ratio of Average Repeating Units Molecular (correspondent from Weight Resin the left in order) (Mw) R-2 60/20/20 12,000 R-7 60/30/10 18,000 R-8 60/20/20 12,000 R-9 60/40 13,000 R-14 60/15/25 12,000 R-17 80/20 15,000

From the results shown in Table 4, it is apparent that the photosensitive compositions in the invention are also excellent as the positive resist compositions in KrF excimer laser exposure.

Examples KrFn-1 to KrFn-7 and Comparative Examples KrFn-1r to KrFn-6r Preparation of Resist:

A negative resist solution having the concentration of solids content of 14 mass % was prepared by dissolving the components in the solvents respectively shown in Table 6 below, and filtrating the solution through a polytetrafluoroethylene filter having a pore size of 0.1 μm.

Each of the prepared negative resist solutions was evaluated in the same manner as in the evaluation by KrF excimer laser exposure in Example KrFp-1, and the results obtained are shown in Table 6.

TABLE 6 KrF Negative Acid Acid Generator Basic Crosslinking Pattern Generator Used in Resin Compound Solvent Agent Collapse Pattern (A) (g) Combination (g) (10 g) (g) Surfactant (mass ratio) (g) (nm) Profile Example No. KrFn-1 A-1 (0.3) z38 (0.4) P-1 PEA (0.02) W-4 A1/B1 CL-1 (3) 68 Rectangle (60/40) KrFn-2 A-2 (0.3) z60 (0.35) P-1 PEA/DIA W-4 A1/B1 CL-4 (4) 63 Rectangle (0.01/0.02) (80/20) KrFn-3 A-4 (0.3) z78 (0.3) P-2 PEA (0.02) W-4 A1/A3 CL-1 (2) 57 Rectangle (60/40) KrFn-4 A-6 (0.4) z38 (0.4) P-2 DIA (0.03) W-4 A1/A3 CL-1 (2) 55 Rectangle (60/40) KrFn-5 A-8 (0.3) z60 (0.3) P-2 PEA (0.02) W-2 A1/B1 CL-1 (2) 69 Rectangle (70/30) KrFn-6 A-32 (0.3) z78 (0.3) P-1 HAP (0.02) W-4 A1/B1 CL-4 (4) 61 Rectangle (60/40) KrFn-7 A-73 (0.5) z38 (0.3) P-2 PEA (0.03) W-4 A1/A3 CL-1 (3) 68 Rectangle (80/20) Comparative Example No. KrFn-1r — (—) z38 (0.4) P-1 HAP (0.02) W-4 A1/B1 CL-1 (2) 92 Reverse (60/40) Taper KrFn-2r TPSB (0.4) z60 (0.4) P-3 DIA (0.03) W-4 A1/B1 CL-1 (2) 98 Taper (60/40) KrFn-3r TPSPB z63 (0.4) P-2 PEA/DIA W-4 A1/B1 CL-4 (4) 102 Taper (0.3) (0.01/0.02) (80/20) KrFn-4r TPS-2 (0.3) z34 (0.25) P-2 PEA (0.03) W-4 A1/A3 CL-4 (4) 102 Taper (60/40) KrFn-5r TPS-3 (0.3) z66 (0.4) P-2 DIA (0.04) W-4 A1/B1 CL-1 (2) 92 Taper (80/20) KrFn-6r TPS-4 (0.3) z60 (0.3) P-3 PEA (0.02) W-2 A1/B1 CL-1 (2) 108 Taper (70/30)

The structures, molecular weights, and molecular weight distributions of the alkali-soluble resins, and crosslinking agents in Table 6 are shown below.

VP-5000 (manufactured by Nippon Soda Co., Ltd.)

From the results shown in Table 6, it is apparent that the photosensitive compositions in the invention are also excellent as the negative resist compositions in KrF excimer laser exposure.

Examples EBp-1 to EBp-7 and Comparative Examples EBp-1r to EBp-6r Preparation of Resist:

A positive resist solution having the concentration of solids content of 12 mass % was prepared by dissolving the components in the solvents respectively shown in Table 4, and filtrating the solution through a polytetrafluoroethylene filter having a pore size of 0.1 μm.

Evaluation of Resist:

The prepared positive resist solution was uniformly coated on a silicon substrate having been subjected to hexamethyldisilazane treatment by a spin coater, and dried by heating on a hot plate at 120° C. for 60 seconds to form a resist film having a thickness of 0.3 μm.

The resist film was irradiated with an electron beam projection lithographic apparatus (accelerating voltage: 100 keV, manufactured by Nikon Corporation), and heated on a hot plate at 110° C. for 90 seconds just after irradiation. Further, the resist film was developed with a 2.38 mass % tetramethyl-ammonium hydroxide aqueous solution at 23° C. for 60 seconds, rinsed with pure water for 30 seconds, and then dried, whereby a line and space pattern was formed. The resist was evaluated as follows.

Pattern Profile:

Taking the exposure amount required to reproduce a dense line and space pattern of 110 nm (pitch: 200 nm) as the optimal exposure amount, and a profile at the optimal exposure amount was observed with a scanning electron microscope.

Pattern Collapse:

With the exposure amount to reproduce a mask of line and space pattern (1/1) of 100 nm being optimal exposure amount, the exposure amount was gradually increased from the optimal exposure amount to make the line width finer, and the line width resolved without causing pattern collapse was taken as the line width of critical pattern collapse. The smaller the value, the finer pattern is resolved without collapsing, that is, pattern collapse occurs with difficulty.

The results obtained are shown in Table 7 below.

TABLE 7 EB Positive Pattern Collapse (nm) Pattern Profile Example No. EBp-1 53 Rectangle EBp-2 59 Rectangle EBp-3 63 Rectangle EBp-4 59 Rectangle EBp-5 65 Rectangle EBp-6 70 Rectangle EBp-7 72 Rectangle Comparative Example No. EBp-1r 100 Taper EBp-2r 103 Taper EBp-3r 103 Taper EBp-4r 110 Taper EBp-5r 110 Taper EBp-6r 106 Taper

From the results shown in Table 7, it is apparent that the photosensitive compositions in the invention are also excellent as the positive resist compositions for electron beam irradiation.

Examples EBn-1 to EBn-7 and Comparative Examples EBn-1r to EBn-6r Preparation of Resist:

A negative resist solution having the concentration of solids content of 12 mass % was prepared by dissolving the components in the solvents respectively shown in Table 6, and filtrating the solution through a polytetrafluoroethylene filter having a pore size of 0.1 μm.

Evaluation of Resist:

The prepared negative resist solution was uniformly coated on a silicon substrate having been subjected to hexamethyldisilazane treatment by a spin coater, and dried by heating on a hot plate at 120° C. for 60 seconds to form a resist film having a thickness of 0.3 μm.

The resist film was irradiated with an electron beam projection lithographic apparatus (accelerating voltage: 100 keV, manufactured by Nikon Corporation), and heated on a hot plate at 110° C. for 90 seconds just after irradiation. Further, the resist film was developed with a 2.38 mass % tetramethyl-ammonium hydroxide aqueous solution at 23° C. for 60 seconds, rinsed with pure water for 30 seconds, and then dried, whereby a line and space pattern was formed. Each resist was evaluated in the same manner as in the evaluation by electron beam exposure in Example EBp-1.

The results obtained are shown in Table 8 below.

TABLE 8 EB Negative Pattern Collapse (nm) Pattern Profile Example No. EBn-1 63 Rectangle EBn-2 65 Rectangle EBn-3 59 Rectangle EBn-4 59 Rectangle EBn-5 60 Rectangle EBn-6 59 Rectangle EBn-7 52 Rectangle Comparative Example No. EBn-1r 100 Taper EBn-2r 107 Taper EBn-3r 107 Reverse taper EBn-4r 94 Taper EBn-5r 107 Taper EBn-6r 103 Taper

From the results shown in Table 8, it is apparent that the photosensitive compositions in the invention are also excellent as the negative resist compositions for electron beam irradiation.

Examples EUV-1 to EUV-7 and Comparative Examples EUV-1r TO EUV-6r

A positive resist solution having the concentration of solids content of 8 mass % was prepared by dissolving the components in the solvents respectively shown in Table 4, and filtrating the solution through a polytetrafluoroethylene filter having a pore size of 0.1 μm.

Evaluation of Resist:

The prepared positive resist solution was uniformly coated on a silicon substrate having been subjected to hexamethyldisilazane treatment by a spin coater, and dried by heating on a hot plate at 120° C. for 60 seconds to form a resist film having a thickness of 0.15 μm. The obtained resist film was subjected to areal exposure with EUV ray (wavelength: 13 nm) with varying exposure amount 0.5 by 0.5 mJ within the range of exposure amount of from 0 to 10.0 mJ, and the resist film was further baked at 110° C. for 90 seconds. After that, a dissolving rate of the resist film at each exposure amount was measured with a 2.38% tetramethylammonium hydroxide (TMAH) aqueous solution, and a sensitivity curve was obtained. In the sensitivity curve, the exposure amount at the time when the dissolving rate of the resist was saturated was taken as sensitivity, and dissolving contrast (γ value) was computed from the gradient of the straight line part of the sensitivity curve. The greater the γ value, the better is the dissolving contrast.

The results of evaluations obtained are shown in Table 9 below.

TABLE 9 Extreme Ultraviolet Radiation Sensitivity (mJ/cm²) γ Value Example No. EUV-1 2.8 17.9 EUV-2 3.5 16.3 EUV-3 3.0 17.0 EUV-4 3.7 17.0 EUV-5 3.5 12.3 EUV-6 2.7 18.1 EUV-7 2.8 19.2 Comparative Example No. EUV-1r 5.9 9.2 EUV-2r 8.9 9.5 EUV-3r 8.8 9.6 EUV-4r 8.2 9.8 EUV-5r 10.0 9.0 EUV-6r 9.9 8.9

From the results shown in Table 9, it can be seen that the resist compositions in the invention are high sensitivity, high contrast and excellent in the characteristic evaluation by irradiation with EUV ray as compared with comparative compositions.

The invention can provide a photosensitive composition showing good pattern profile and pattern collapse resistance, and improved in sensitivity and dissolution contrast in EUV ray exposure, and a pattern-forming method using the photosensitive composition. Further, the invention can provide a positive resist composition suitable for immersion exposure having good performances as described above even in immersion exposure, and a pattern-forming method using the positive resist composition.

The entire disclosure of each and every foreign patent application from which the benefit of foreign priority has been claimed in the present application is incorporated herein by reference, as if fully set forth. 

1. A photosensitive composition, which comprises (A) a compound capable of generating an organic acid represented by formula (I) upon irradiation with actinic ray or radiation: Z-A-X—B—R—(Y)_(n)  (I) wherein Z represents an organic acid group; A represents a divalent linking group; X represents a divalent linking group having a hetero atom; B represents an oxygen atom or —N(R_(x))—; R_(x) represents a hydrogen atom or a monovalent organic group; R represents a monovalent organic group substituted with Y, and when B represents —N(R_(x))—, R and R_(x) may be bonded to each other to form a cyclic structure; Y represents —COOH or —CHO, and when a plurality of Y's are present, the plurality of Y's may be the same or different; and n represents an integer of from 1 to
 3. 2. The photosensitive composition according to claim 1, wherein A contains a fluorine atom.
 3. The photosensitive composition according to claim 2, wherein A contains a carbon atom bonding to Z, and the carbon atom bonding to Z has a fluorine atom.
 4. The photosensitive composition according to claim 1, wherein A represents an alkylene group.
 5. The photosensitive composition according to claim 4, wherein from 30 to 100% of hydrogen atoms contained in the alkylene group represented by A are substituted with fluorine atoms.
 6. The photosensitive composition according to claim 1, wherein Z is a sulfo group or a carboxyl group.
 7. The photosensitive composition according to claim 1, wherein X is selected from the group consisting of —SO₂—, —SO— and —CO—.
 8. The photosensitive composition according to claim 1, wherein the compound capable of generating an organic acid represented by formula (I) upon irradiation with actinic ray or radiation is a sulfonium salt compound of an organic acid represented by formula (I) or an iodonium salt compound of an organic acid represented by formula (I).
 9. A pattern-forming method, which comprises: forming a photosensitive film with a photosensitive composition according to claim 1; and exposing and developing the photosensitive film.
 10. An organic acid represented by formula (I) and a metal salt thereof: Z-A-X—B—R—(Y)_(n)  (I) wherein Z represents an organic acid group; A represents a divalent linking group; X represents a divalent linking group having a hetero atom; B represents an oxygen atom or —N(R_(x))—; R_(x) represents a hydrogen atom or a monovalent organic group; R represents a monovalent organic group substituted with Y, and when B represents —N(R_(x))—, R and R_(x) may be bonded to each other to form a cyclic structure; Y represents —COOH or —CHO, and when a plurality of Y's are present, the plurality of Y's may be the same or different; and n represents an integer of from 1 to
 3. 11. A sulfonium salt compound of an organic acid represented by formula (I) or an iodonium salt compound of an organic acid represented by formula (I): Z-A-X—B—R—(Y)_(n)  (I) wherein Z represents an organic acid group; A represents a divalent linking group; X represents a divalent linking group having a hetero atom; B represents an oxygen atom or —N(R_(x))—; R_(x) represents a hydrogen atom or a monovalent organic group; R represents a monovalent organic group substituted with Y, and when B represents —N(R_(x))—, R and R_(x) may be bonded to each other to form a cyclic structure; Y represents —COOH or —CHO, and when a plurality of Y's are present, the plurality of Y's may be the same or different; and n represents an integer of from 1 to
 3. 